20
12
Light and Lighting
An inquiry-based unit for primary and elementary students in an after-school setting. The unit provides background information and hands-on activities on the energy of light and lighting.
Grade Level: n Primary n Elementary
Subject Areas: n Science n Social Studies n Math n Language Arts n Technology
-20
13
NEED Mission Statement
Teacher Advisory Board Shelly Baumann Rockford, MI
Matthew Inman Spokane, Washington
Constance Beatty Kankakee, IL
Michelle Lamb Buffalo Grove, IL
Sara Brownell Canyon Country, CA
Barbara Lazar Albuquerque, NM
Loree Burroughs Merced, CA
Robert Lazar Albuquerque, NM
Amy Constant Raleigh, NC
Leslie Lively Reader, WV
Joanne Coons Clifton Park, NY
Mollie Mukhamedov Port St. Lucie, FL
Nina Corley Galveston, TX
Don Pruett Sumner, WA
Regina Donour Whitesburg, KY
Josh Rubin Palo Alto, CA
Linda Fonner New Martinsville, WV
Joanne Spaziano Cranston, RI
Samantha Forbes Vienna, VA
Gina Spencer Virginia Beach, VA
Viola Henry Thaxton, VA
Tom Spencer Chesapeake, VA
Robert Hodash Bakersfield, CA
Joanne Trombley West Chester, PA
DaNel Hogan Kuna, ID
Jim Wilkie Long Beach, CA
Greg Holman Paradise, CA
Carolyn Wuest Pensacola, FL
Linda Hutton Kitty Hawk, NC
Wayne Yonkelowitz Fayetteville, WV
The mission of The NEED Project is to promote an energy conscious and educated society by creating effective networks of students, educators, business, government and community leaders to design and deliver objective, multisided energy education programs.
Teacher Advisory Board Statement In support of NEED, the national Teacher Advisory Board (TAB) is dedicated to developing and promoting standardsbased energy curriculum and training.
Permission to Copy NEED materials may be reproduced for non-commercial educational purposes.
Energy Data Used in NEED Materials NEED believes in providing the most recently reported energy data available to our teachers and students. Most statistics and data are derived from the U.S. Energy Information Administration’s Annual Energy Review that is published in June of each year. Working in partnership with EIA, NEED includes easy to understand data in our curriculum materials. To do further research, visit the EIA web site at www.eia.gov. EIA’s Energy Kids site has great lessons and activities for students at www.eia.gov/kids.
1.800.875.5029 www.NEED.org © 2012
Printed on Recycled Paper
2
Light and Lighting
Light and Lighting
Table of Contents Correlations to National Science Education Standards
4
Making Shadows
36
Materials
6
Where is the Sun?
37
Teacher Guide
7
Hand Shadows
38
Lab Safety Rules
15
Spectroscope
39
Student Informational Text
16
Reflection
40
Thermometer
22
Maze 1
41
Solar Energy to Heat
23
Maze 2
42
Solar Balloon
24
Solar House
43
Radiometer
25
Photovoltaic Cells Explanation
44
Radiometer Explanation
26
Comparing Light Bulbs
45
Lightsticks
27
Facts of Light
46
NaturePrint® Paper
28
Facts of Light Comparison
47
Glow Toys
32
Light Bulb Comparison
48
Glow Toy Explanation
33
Home Energy Use Survey
49
UV Beads
34
Light and Lighting Survey
50
How Light Travels
35
Evaluation Form
51
Developed in partnership with the U.S. Department of Energy, National Association of State Universities and Land-Grant Colleges, and the National 4-H Council’s 4-H Afterschool program.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
3
Correlations to National Science Education Standards: Grades K-4 This book has been correlated to National Science Education Content Standards. For correlations to individual state standards, visit www.NEED.org.
Unifying Concepts and Processes Systems, Order, and Organization
The goal of this standard is to think and analyze in terms of systems, which will help students keep track of mass, energy, objects, organisms, and events referred to in the content standards. Science assumes that the behavior of the universe is not capricious, that nature is the same everywhere, and that it is understandable and predictable. Students can develop an understanding of order––or regularities––in systems, and by extension, the universe; then they can develop understanding of basic laws, theories, and models that explain the world. Prediction is the use of knowledge to identify and explain observations, or changes, in advance. The use of mathematics, especially probability, allows for greater or lesser certainty of prediction. Order—the behavior of units of matter, objects, organisms, or events in the universe—can be described statistically. Probability is the relative certainty (or uncertainty) that individuals can assign to selected events happening (or not happening) in a specified time or space. Types and levels of organization provide useful ways of thinking about the world.
Evidence, Models, and Explanation
Evidence consists of observations and data on which to base scientific explanations. Using evidence to understand interactions allows individuals to predict changes in natural and designed systems.
Change, Constancy, and Measurement
Although most things are in the process of change, some properties of objects and processes are characterized by constancy; for example, the speed of light, the charge of an electron, and the total mass plus energy of the universe. Energy can be transferred and matter can be changed. Nevertheless, when measured, the sum of energy and matter in systems, and by extension in the universe, remains the same. Changes can occur in the properties of materials, position of objects, motion, and form and function of systems. Interactions within and among systems result in change. Changes in systems can be quantified and measured. Mathematics is essential for accurately measuring change. Different systems of measurement are used for different purposes. An important part of measurement is knowing when to use which system.
Evolution and Equilibrium
Equilibrium is a physical state in which forces and changes occur in opposite and offsetting directions. Interacting units of matter tend toward equilibrium states in which the energy is distributed as randomly and uniformly as possible.
Content Standard A | Science as Inquiry Abilities Necessary to do Scientific Inquiry
Ask a question about objects, organisms, and events in the environment. Plan and conduct a simple investigation. Employ simple equipment and tools to gather data and extend the senses. Use data to construct a reasonable explanation. Communicate investigations and explanations.
Understandings about Scientific Inquiry
Scientific investigations involve asking and answering a question and comparing the answer with what scientists already know. Simple instruments such as magnifiers, thermometers, and rulers provide more information than using only senses.
4
Light and Lighting
Correlations to National Science Education Standards: Grades K-4 This book has been correlated to National Science Education Content Standards. For correlations to individual state standards, visit www.NEED.org.
Content Standard B | Physical Science Properties of Objects and Materials
Objects have many observable properties, including size, weight, shape, color, temperature, and the ability to react with other substances. Those properties can be measured using tools such as rulers, balances, and thermometers. Objects are made of one or more materials, such as paper, wood, and metal. Objects can be described by the properties of the materials from which they are made, and those properties can be used to separate or sort a group of objects or materials. Materials can exist in different states—solid, liquid, and gas. Some common materials, such as water, can be changed from one state to another by heating or cooling.
Light, Heat, Electricity, and Magnetism
Light travels in a straight line until it strikes an object. Light can be reflected by a mirror, refracted by a lens, or absorbed by the object. Heat can be produced in many ways, such as burning, rubbing, or mixing one substance with another. Heat can move from one object to another by conduction.
Content Standard A | Science as Inquiry Abilities Necessary to do Scientific Inquiry
Identify questions that can be answered through scientific inquiry. Design and conduct a scientific investigation. Use appropriate tools and techniques to gather, analyze, and interpret data. Develop descriptions, explanations, predictions, and models using evidence. Think critically and logically to make the relationships between evidence and explanations. Recognize and analyze alternative explanations and predictions. Communicate scientific procedures and explanations. Use mathematics in all aspects of scientific inquiry.
Correlations to National Science Education Standards: Grades 5-8 This book has been correlated to National Science Education Content Standards. For correlations to individual state standards, visit www.NEED.org.
Content Standard B | Physical Science Transfer of Energy
Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical. Energy is transferred in many ways. Heat moves in predictable ways, flowing from warmer objects to cooler ones, until both reach the same temperature. Light interacts with matter by transmission (including refraction), absorption, or scattering (including reflection). The sun is the major source of energy for changes on the earth’s surface. The sun loses energy by emitting light. A tiny fraction of that light reaches earth, transferring energy from the sun to the earth. The sun’s energy arrives as light with a range of wavelengths.
Content Standard C | LIFE Science Populations and Ecosystems
For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis. The energy then passes from organism to organism in food webs.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
5
Materials Activity
Materials Needed
Light to Heat—Using Thermometers
Demonstration and student thermometers
Black and white construction paper Scissors Colored pencils Black and white paints (optional)
Light to Heat—Solar Balloons and Radiometer
Solar balloons Radiometer
Colored pencils
Light and Chemical Changes—Lightsticks and NaturePrint® Paper
10 Lightsticks NaturePrint® Paper
Ice water Warm water Scissors Paper Cups
Stored Light and Colors—Glow Toys and UV Beads
Glow toys UV beads Pipe cleaners
Sunscreen (spray) Ziplock bag Black construction paper Tape Scissors
Shadows and Light Travels
Flashlights
Pieces of cardboad Sharp pencils Clay Crayons Rulers Scissors
Light Can Be Separated
Spectroscopes Flashlights
Colored pencils or crayons Spray bottles with water
Light Can Be Reflected
Flashlights Mirrors
Yarn
Light Can Be Turned Into Electricity
PV cell kit
Sharp pencils Clay Shoe boxes Scissors Crayons
It Takes Energy to Make Light
Lamp Incandescent light bulb Compact fluorescent light bulb
Calculators
We Can Save Energy—Home Energy Survey
6
Materials In Kit
Paper Pencils
Light and Lighting
Teacher Guide
An inquiry-based unit for primary and elementary students that provides background information and hands-on activities on the energy of light and lighting.
Grade Level
Overview and Preparation Read the guide and become familiar with the information, activities, and equipment in the kit. Gather the materials needed for activities using the chart on page 6. Practice the experiments to gain an understanding of possible outcomes, difficulties, and questions. Make copies of student worksheets and the informational text, as needed.
Primary K-2 Elementary 3-5
Time Approximately 10-12 one-hour sessions
Make two copies of Light and Lighting Survey on page 50 for each student. One copy can be used as a pre-assessment, the other, a post-assessment of student understanding. Allow the students to take their work home each day to share with their families. With all of the activities, give older students responsibility for working with the younger students to help them understand and complete the experiments and student worksheets. Make sure the students understand the applicable Lab Safety Rules on page 15.
Activity 1: Light to Heat—Using Thermometers Concepts Light is radiant energy that travels in waves. Light waves can be refracted, reflected, and absorbed by substances. When light is absorbed by substances, it is often transformed into thermal energy (heat). We can measure heat with a thermometer.
Materials Demonstration and student thermometers Black and white paper Scissors Colored pencils
Black and white paint (optional) Thermometer worksheet, page 22 Solar Energy to Heat worksheet, page 23
Procedure 1. Set up five centers, each with black and white construction paper, scissors, colored pencils, and two students thermometers. 2. Introduce the activity using the pertinent information in the informational text (pages 16-21). 3. Use the demonstration thermometer to show the students how to read a thermometer, explaining the two scales—Fahrenheit and Celsius. 4. Have the students complete the Thermometer and Solar Energy to Heat activities. 5. Discuss the students’ answers to the Conclusion questions.
Optional: Have each student paint one hand with black paint and the other with white paint and hold their hands in the sun for a few moments. Have them observe the difference in temperature and explain why one hand feels hotter than the other.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
7
Activity 2: Light to Heat—Solar Balloons and Radiometer Concepts Light waves can be refracted, reflected, and absorbed by substances. When light is absorbed by substances, it is often transformed into thermal energy (heat). When substances absorb light and turn it into heat, they usually expand.
Materials Solar balloons Radiometer Colored pencils
Solar Balloon worksheet, page 24 Radiometer worksheet, page 25 Radiometer Explanation, page 26
Procedure 1. Introduce the activity by reminding students that black objects absorb light energy and white objects reflect light energy. 2. Go outside to fly the solar balloons on a sunny day, using the directions on page 24. 3. Demonstrate the radiometer by putting it in the sun (or in a bright light) and letting the students observe and complete the Radiometer activity. 4. Discuss the students’ answers to the Conclusion and Explanation questions. 5. Demonstrate or display the Radiometer Explanation to further understanding of how the radiometer works.
Activity 3: Light and Chemical Changes—Lightsticks and NaturePrint® Paper Concepts Light can produce chemical changes in substances. Chemical reactions can produce light. Adding thermal energy (heat) can speed up chemical reactions; removing thermal energy (cooling) can slow them down.
Materials 10 Lightsticks 5 Cups of ice water 5 Cups warm water NaturePrint® Paper
Scissors Paper Lightsticks activity, page 27 NaturePrint® Paper activity, pages 28-31
Procedure 1. Set up five centers, with one cup each of ice water and warm water and two lightsticks. 2. Introduce the activity to the students, explaining that chemical reactions can produce light and that light can cause chemical changes. 3. Divide the students into five groups, have them go to the centers. Give each student a copy of the activity sheets. 4. Instruct the students to examine the lightsticks and then break the lightsticks and shake them. Instruct students to put one in the cup of ice water and one in the cup of warm water, and observe the amount of light produced. Discuss. You can put the lightsticks in a freezer to save if you like; the cold will slow the chemical reaction. 5. Have each student cut out a sun template or create his/her own design to use with the NaturePrint® Paper. Students can also use their own items to place on top. 6. Give each student a piece of the NaturePrint® Paper and follow the directions on the worksheet and the package to make the prints. Allow the students to take their finished projects home. 7. Discuss the students’ answers to the Conclusion and Extension questions.
8
Light and Lighting
Day 4: Stored Light and Colors—Glow Toys and UV Beads Concepts Light can produce chemical changes in substances. Some substances can store light and release it as light at a later time.
Materials Tape Scissors Glow Toys worksheet, page 32 Glow Toy Explanation, page 33 UV Beads worksheet, page 34
Glow toys UV beads Pipe cleaners Sunscreen (spray) Ziplock bag Black construction paper
Procedure 1. Set up five centers with paper, scissors, and tape. 2. Introduce the activities to the class, distributing pages 32 and 34. 3. Show the students a glow toy and instruct them to make pouches big enough to hold the glow toys with the black construction paper and tape. 4. Distribute two glow toys to each center, instructing the students to place one in the pouch. 5. Distribute five beads and one pipe cleaner to each student. Instruct the students to string their beads onto the pipe cleaners and make bracelets. 6. Place several beads into the ziplock bag. Show students the bag and then spray both sides of the bag with liberal amounts of sunscreen. 7. Take students outside to conduct the glow toy and UV bead experiments. Have students observe the bag of beads and note differences in the beads compared to their bracelet. Discuss. 8. Take the students into a darkened room to complete the glow toy activity. Use or project the Glow Toy Explanation to further understanding of how glow-in-the-dark substances work. 9. Allow the students to take their bracelets and a glow toy home. 10. Discuss the students’ answers to the Conclusion and Extension questions.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
9
Activity 5: Light Travels and Making Shadows Concepts Light waves travel in a straight line. A shadow is an area where an object is blocking the light. The size of a shadow changes according to the direction and angle of the light source.
Materials Flashlights Pieces of cardboard Sharp pencils Clay Crayons Rulers
Scissors How Light Travels worksheet, page 35 Making Shadows worksheet, page 36 Where is the Sun? worksheet, page 37 Hand Shadows handout, page 38
Procedure 1. Set up four centers with a flashlight, a sharp pencil, a new crayon, and a piece of clay. 2. Place the students at the centers, distribute worksheets, and introduce the activity. 3. Instruct the students to complete the How Light Travels activity. Discuss the Conclusion questions. 4. Take the students outside to observe shadows. 5. Instruct the students to complete the Making Shadows and the Where is the Sun? activities. If time allows, have students create the hand shadows on page 38. 6. Discuss the students’ answers to the Conclusion and Extension questions. 7. Allow the students to take page 38 home to complete with their families.
Activity 6: Light Can Be Separated Concepts Visible light is made of many wavelengths of radiant energy. Visible light can be separated into different colors of light according to their wavelengths.
Materials Spectroscopes Flashlights Colored pencils or crayons Spray bottles with water Spectroscope worksheet, page 39
Procedure 1. Introduce the activity with a discussion of rainbows. 2. Distribute the Spectroscope worksheet to the students. 3. Allow each student to look through a spectroscope and instruct the students to draw the colors they see on their worksheets. 4. Go outside in the sun and use the spray bottles to make rainbows. 5. Discuss the students’ answers to the Conclusion and Extension questions.
10
Light and Lighting
Activity 7: Light Can Be Reflected Concepts Light travels in a straight line. Light waves can be reflected. The angle of incidence of light is equal to the angle of reflection.
Materials Flashlights Mirrors Yarn Reflection and Maze worksheets, page 40-42
Procedure 1. Introduce the activity to the students with a discussion about mirrors and other materials that reflect light. Distribute the Reflection activity. 2. Have the students choose partners and conduct the experiment. 3. Discuss the students’ answers to the Conclusion questions. 4. Distribute the mazes. Have the students complete Maze 1 and take Maze 2 home to complete with their families.
Activity 8: Light Can Be Turned Into Electricity Concepts A PV cell can convert light into electricity. Electricity can be used to perform work.
Materials PV cell kit Sharp pencils Clay 5 Shoe boxes
Scissors Crayons Photovoltaic Cells Explanation, page 44 Solar House worksheet, page 43
Procedure 1. Set up five centers with shoe boxes, scissors, crayons, and pencils. 2. Introduce the activity by discussing PV cells, how they work, and where people see them. 3. Distribute the Solar House activity. Have the students go to the centers and make houses out of the cardboard boxes by adding windows and doors. Take the houses outside on a sunny day. 4. Install the PV cell with the fan on each house in turn to show how a PV cell turns light into electricity. 5. Discuss places where PV cells would be very helpful, such as in rural or remote areas without access to the electricity grid, and on road signs. Use or project the Photovoltaic Cells Explanation to futher student understanding of how a PV cell works.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
11
Activity 9: It Takes Energy To Make Light Concepts Some light bulbs produce more heat than others. Some light bulbs are more energy efficient than others. Life cycle cost is the total cost of using an appliance and is more important than purchase price.
Materials Lamp Incandescent light bulb Compact fluorescent light bulb Calculators
Light Bulb Comparison, page 48 Comparing Light Bulbs worksheet, page 45 Facts of Light worksheets, pages 46-47
Procedure 1. Set up the lamp so that it is convenient to all of the students. 2. Distribute pages 45-47 and introduce the activity by talking about lighting, how many light bulbs are in the students’ homes, and how many use compact fluorescent light bulbs at home. Emphasize that they must pay for the electricity to operate lights. 3. Conduct the comparison activity according to the directions on page 45, allowing all of the students to observe. 4. Have the students read the Facts of Light individually or as a class. Complete the Facts of Light activity as a group. Discuss reasons why more people don’t use compact fluorescent light bulbs—the initial cost of the bulbs, limited understanding of life cycle costs, buying habits, not enough information. Use or project Light Bulb Comparison to help students with the discussion. 5. Make sure the students take their worksheets home to discuss with their families.
Activity 10: We Can Save Energy—Home Energy Survey Concepts We use energy in many ways to make our lives more comfortable and efficient. There are many ways we waste energy. Using energy costs money. There is not an infinite amount of usable energy. We need to conserve energy whenever we can.
Materials Paper Pencils Home Energy Survey, page 49
Procedure 1. Ask students to brainstorm ways they use and waste energy at home. 2. Have the students brainstorm a list of ways that they could save energy at home. 3. Distribute the survey and discuss their predictions. 4. Have the students take the survey home to complete with their families. Have a discussion with students about their results.
Evaluation Distribute Light and Lighting Survey to students as a post-assessment. If you have young students, you can read the questions to them. Collect the forms and send them to NEED to evaluate the program. Together with the students, complete the Evaluation Form on page 51 and return to The NEED Project, P.O. Box 10101 Manassas, Virginia 20108.
12
Light and Lighting
Answer Key Thermometer, page 22 Water Boils—212°F, 100°C Human Body—98.6°F, 37°C Water freezes—32°F, 0°C
Solar Energy to Heat Worksheet, page 23 Which color absorbed the most energy? What evidence from the activity shows you this? Black should absorb the most energy. Students should find that the black covered thermometer got warmer. How should this information affect your clothing choices? What color will you wear on a sunny day? Student answers should reflect that wearing dark colors during summer might make them hotter. Which will be hotter on a sunny day, a car with a dark interior, or a car with a light tan interior? How do you know? Student answers should reflect that a car with lighter interior will be less hot.
Solar Balloon, page 24 Explain what happened to the air inside the balloon and why it rose? The air in the balloon was heated because the balloon is black and absorbed the light from the sun and changed it to heat. Warm air rises and the air inside the balloon became warmer than the air around it causing it to rise. Will the balloon fly on a sunny but very cold winter day? Yes the balloon will fly on a sunny but cold day.
Radiometer, page 25 Explain how the radiometer turns the sun’s energy into motion. Light energy from the sun enters the radiometer, the light energy is changed to heat. The black side of the vane absorbs more of this energy and heats up the air in the radiometer. The air molecules then speed up and begin bouncing off of the radiometer vanes. The white sections don’t rebound as much of the air molecules because they reflect more energy. The black side rebounds more of the air molecules because it’s warmer. One side is pushing the energy more than the other, causing the radiometer to spin.
Lightsticks, page 27 Explain how heat affects the chemical reaction in a light stick. Student answers should reflect that the light stick glows more brightly in the hot water, and in the cold water its light is dimmed. Additional heat speeds up the chemical reaction in a light stick causing more light to be produced, while removing heat slows it down.
NaturePrint® Paper, page 28 Describe how your NaturePrint® Paper changed over time. Explain why you think this occurred. The paper, when placed in the light, goes through a chemical reaction causing it to change colors. Students should say that their papers had designs imprinted or left behind. The areas shaded by objects did not change colors, while the surrounding areas did.
Glow Toys, page 32 How does energy from the sun affect a glow toy? Student answers should reflect that light from the sun causes the glow toy to store and release light energy later. Glow toys not exposed to light will not glow because they did not store any energy.
UV Beads, page 34 What happened to your beads outside in the sun? The sun should cause the beads to change color because the beads undergo a chemical reaction when exposed to UV radiation. How does sunscreen affect the UV beads? The beads change color, like your skin, when exposed to UV rays. If sunscreen is applied, less UV radiation gets through, causing less of a color change.
How Light Travels, page 35 How does light travel? Light travels in a straight line, but is capable of spreading out. Light waves can be absorbed, reflected, or refracted. ©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
13
Making Shadows, page 36 What variables affect the size and shape of an object’s shadow? Possible student answers could include: how far away the light is from the object, the type of light, the shape of the object, the angle of the light or the object, the size of the object, etc.
Where is the Sun?, page 37 Cactus 1: overhead Cactus 2: front, right, high Cactus 3: back, right, high Cactus 4: front, left, low
Maze 1 Solve the maze of mirrors! Draw the reflected light wave as it is reflected from mirror to mirror until you reach the last mirror before the light wave leaves the page. This is the final mirror. HINTS: Every mirror is part of the maze. Focus on the middle of the mirrors.
Spectroscope, page 39 What colors of light make up visible light? Visible light is made of the colors in the rainbow, or ROYGBIV. Does a rainbow have the same colors in the same order as a spectroscope? Students should be able to see that the order is the same in both items.
Reflection, page 40 How is light reflected? Light bounces off of shiny surfaces in a straight line. How does the angle of the light traveling to the mirror compare to the angle of the reflected light? Students should be able to describe the angles as being similar because of the lines they made with their yarn.
Maze 1 and 2, pages 41-42
Maze 2 Solve the maze of mirrors! Draw the reflected light wave as it is reflected from mirror to mirror until you reach the last mirror before the light wave travels off the page. This is the final mirror. Every mirror is a part of the maze.
Answer keys to the right.
Solar House, page 43 How does the angle of the PV cell to the sun affect the amount of electricity it produces? Student answers should reflect that different angles make the fan spin faster or slower. The more direct light the cell receives, the faster the fan will turn because it is creating more electricity.
Comparing Light Bulbs, page 45 Which bulb produced more light? More heat? Both bulbs should produce the same amount of light after a short time. However, the incandescent will produce much more heat. Which bulb do you think is more energy efficient? Explain what you think using your observations above. The CFL is more efficient because it produces the same amount of light but wastes less energy on heat.
Facts of Light, page 47 INCANDESCENT BULB
HALOGEN
COMPACT FLUORESCENT (CFL)
$12.50
$24.90
$7.50
$40.00
1,500 kWh
1,075 kWh
325 kWh
300 kWh
Cost of bulbs for 25,000 hrs of light Total kWh Consumption
LIGHT EMITTING DIODE (LED)
Cost of electricity
$180.00
$129.00
$39.00
$36.00
Life Cycle Cost
$192.50
$153.90
$46.50
$76.00
2,400 lbs of carbon dioxide
1,720 lbs of carbon dioxide
520 lbs of carbon dioxide
480 lbs of carbon dioxide
Pounds of carbon dioxide produced
Light and Lighting Survey, page 50 1. Girl in dark clothing 2. Boy farthest from the sun
14
3. True 4. True
5. False 6. False
7. True 8. CFL Light and Lighting
Lab Safety Rules Eye Safety
Always wear safety glasses when performing experiments.
Fire Safety
Do not heat any substance or piece of equipment unless specifically instructed to do so.
Be careful of loose clothing. Do not reach across or over a flame.
Keep long hair pulled back and secured.
Do not heat any substance in a closed container.
Always use tongs or protective gloves when handling hot objects. Do not touch hot objects with your hands.
Keep all lab equipment, chemicals, papers, and personal items away from the flame.
Extinguish the flame as soon as you are finished with the experiment and move it away from the immediate work area.
Heat Safety
Always use tongs or protective gloves when handling hot objects and substances.
Keep hot objects away from the edge of the lab table––in a place where no one will accidentally come into contact with them.
Do not use the steam generator without the assistance of your teacher.
Remember that many objects will remain hot for a long time after the heat source is removed or turned off.
Glass Safety
Never use a piece of glass equipment that appears to be cracked or broken.
Handle glass equipment carefully. If a piece of glassware breaks, do not attempt to clean it up yourself. Inform your teacher.
Glass equipment can become very hot. Use tongs or gloves if glass has been heated.
Clean glass equipment carefully before packing it away.
Chemical Safety
Do not smell, touch, or taste chemicals unless instructed to do so.
Keep chemical containers closed except when using them.
Do not mix chemicals without specific instructions.
Do not shake or heat chemicals without specific instructions.
Dispose of used chemicals as instructed. Do not pour chemicals back into a container without specific instructions to do so.
If a chemical accidentally touches your skin, immediately wash the area with water and inform your teacher.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
15
Student Informational Text Light is energy
We use light energy every day. Without light, our lives would be very different. Close your eyes and think about a world without light.
Sunlight
We use light energy for more than seeing. The energy in light helps plants grow. Doctors use special light to help in surgery. We can also use light to make products and electricity.
Light Is Energy In Waves What is light? Light is energy that travels in waves. All the energy we get from the sun travels in waves. Some of that energy is in light waves we can see—it is visible light. Some is in waves we can’t see. We can’t see infrared waves, but they can warm us when they touch our skin. We can’t see ultraviolet waves, but they can burn our skin.
Wave Measurements
We measure waves by the distance from the top, or crest, of one wave to the top of the next. This distance is called its wavelength. The shorter the wavelength, the more energy the wave has. Some waves of energy—like radio waves—are very long. Radio waves can be a mile long. Other waves are very short—like visible light waves and x-rays. There are about 50,000 waves in an inch of visible light.
CREST
LENGTH
HEIGHT
TROUGH
Energy in Waves
Radio waves
16
Television waves
Microwaves
Infrared waves
VISIBLE LIGHT
Ultraviolet
Xrays
Light and Lighting
Light Waves Travel In Straight Lines Light waves travel in straight lines. They do not change direction unless they are reflected or refracted. When light from the sun hits a tree, it cannot pass through it. It cannot go around the tree. Some of the light is absorbed by the tree and the rest is reflected back into the air. An area without light is made—a shadow. Thousands of years ago, early Egyptians studied shadows. They knew the sun travels the same path in the sky everyday. They knew that shadows change as the sun moves across the sky. They used this knowledge to develop a tool to tell time—a sundial. They placed a stick in the ground. The position and length of the stick’s shadow told the people the time.
An Eclipse Is A Shadow Sometimes the moon moves between the Earth and the sun. The sun’s light cannot pass through the moon to reach the Earth. A large shadow covers the Earth. This is called a solar eclipse. During an eclipse, some parts of the Earth get no light at all. They become as dark as night. This area is called the umbra. Some parts of the Earth get some light. They are in part shadow, part light. This area is called the penumbra.
Eclipse PENUMBRA UMBRA the sun is the sun is totally hidden partly hidden
Sun Moon
When Light Waves Hit Substances Light waves travel in a straight line. When light waves hit something, three things can happen. The light can travel through a substance and bend—be refracted. Light passing through transparent substances like water is bent, or refracted. Light waves can enter a substance and be absorbed. Plants absorb some light waves and convert them into sugars through photosynthesis. Light waves can also bounce off a substance—be reflected. A mirror reflects light waves. Many substances absorb some light waves and reflect others.
Earth
Photosynthesis In the process of photosynthesis, plants convert radiant energy from the sun into chemical energy in the form of glucose (or sugar). RADIANT ENERGY
RADIANT ENERGY
CARBON DIOXIDE OXYGEN
OXYGEN
WATER GLUCOSE
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
CARBON DIOXIDE WATER
17
Light Has Many Wavelengths Visible light—the wave energy we can see—is made of many colors. Every color has a different wavelength. The longest wavelengths are reds. The medium wavelengths are yellows. The shortest wavelengths are violets. All of the colors mixed together make white light.
A Prism Separates Light Waves A prism is a piece of clear glass or plastic that bends light waves as they pass through it. A prism is often shaped like a triangle. A prism can separate visible light into its different wavelengths. It can separate all of the colors that make up white light. A prism bends—or refracts—light waves. The wavelengths of each color bend at a different angle. The light that goes into the prism spreads out as it leaves the prism. Have you ever seen a rainbow? Rainbows are formed when the sun shines while it is raining. Drops of rain act like tiny prisms to bend the sunlight. The raindrops separate the light waves into colors.
Color Wavelengths RED ORANGE YELLOW GREEN BLUE INDIGO VIOLET
Prism
Water refracts light waves, too. Light can pass through water, but it bends as it goes through. Have you ever noticed that things look different in the bathtub or swimming pool? The water is bending the light. The light waves are refracted as they pass through the water.
We Can Bend Light With a Lens We can use pieces of glass in different shapes—called lenses—to bend light.
ite wh
re oran d yello ge gree w blue n indi viol go et
ht lig
A convex lens is thicker in the middle than on the ends. It bends light waves toward a point. A convex lens can make objects look larger. A concave lens is thinner in the middle than on the ends. It spreads out light waves that pass through it. A concave lens can make objects look smaller.
18
Refraction Convex lens
Concave lens
Light and Lighting
We Use Lenses Every Day To Refract Light The human eye has a convex lens. The eye sees light waves bouncing off an object. The lens in the eye refracts the light waves as they pass through it. The light waves hit the retina in the back of the eye. The light waves make an image of the object on the retina. The image on the retina is upside down. When we are babies, our brains quickly learn to turn the images around. Otherwise, everything would look upside down. If our eyes are not the right shape, we cannot see clearly. The image does not focus on the retina. It is blurry. We can use lenses in eye glasses to help us see better. The lenses refract the light waves so that they focus the image on the retina. Contact lenses do the same thing.
How Your Eye Works
RETINA LENS
IMAGE OF OBJECT
OBJECT
LIGHT REFLECTED FROM OBJECT
A magnifying glass is a convex lens with a handle. Telescopes and microscopes have convex lenses, too. They can make small objects look larger or distant objects appear closer. The picture on the bottom of the page shows how a convex lens works. Light waves bounce off an object and bend as they pass through the lens. The eye sees the larger image shown by the dotted lines.
A magnifying glass is a convex lens.
Convex Lens
CONVEX LENS
A convex lens refracts light and makes objects appear larger.
LARGER IMAGE
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
HUMAN EYE
ACTUAL OBJECT
1.800.875.5029
www.NEED.org
19
Light Waves Can Be Reflected
DISCO BALL
How do we see things? We see the light waves that bounce off things—the light that is reflected by substances. When you look at an object, you are really seeing reflected light waves. Think about it. When there are no light waves, you can’t see anything. When you look in the mirror, the image you see is made by light waves. Light from all around you bounces off of you. Some of the light waves travel toward the mirror. The mirror reflects the light waves. Some of the light waves from the mirror travel toward your eyes. Your eyes see these reflected light waves.
Reflection Of Light Is Predictable Light waves don’t just bounce around. They are reflected at angles we can predict. The reflection of light is a lot like bouncing a round ball on a smooth surface. If you drop the ball straight down, it will bounce straight back up. If you bounce the ball away from you, it will continue to move away from you in a straight line. It won’t bounce to the left or right, or back toward you. It bounces away at the same angle you throw it.
Reflection of Light LIG
HT
WA VE
VE WA T H
Angle A = Angle B
ED ECT
LIG
FL
RE Angle A
Light waves are reflected in the same way. Light waves travel in straight lines. When a light wave hits an object and is reflected, it will be reflected in a straight line. If the light wave hits an object at an angle, it will WHO IS COOLER? be reflected at the same angle.
Angle B MIRROR
Look at the picture to the right. The light wave is traveling toward the mirror at an angle—labeled Angle A. When the light wave hits the mirror, it is reflected at an angle—labeled Angle B. Both angles are the same. Angle A equals Angle B.
Light Waves Can Be Absorbed We know that light waves can pass through a substance and bend—be refracted. Water and prisms refract light waves. We also know that light waves can hit something and be reflected. We can see objects only because light waves are reflected off the objects and into our eyes. Light waves can also enter a substance and change into other forms of energy. The light energy can be absorbed by the substance. When we are in the sun, some of the light waves enter our skin and turn into heat. Our bodies absorb some of the light waves.
20
Light and Lighting
Black And White Most substances reflect some light waves and absorb others. That’s why we see colors! Visible light is made of every color. Every color has a different wavelength.
Black and White
When a substance absorbs all wavelengths of visible light, the substance looks black. No light waves are reflected to reach our eyes. The light waves—which are waves of energy—enter the substance. The substance changes the light energy to other forms of energy. When a substance reflects all wavelengths of visible light, the substance looks white. Have you heard that dark colored clothes make you hotter in the sun? That’s because dark colors absorb light waves and light colors reflect them.
Seeing Colors We see many colors because most substances absorb some wavelengths of light and reflect others. We see the colors that are reflected by the substances. A rose looks red because it is reflecting the red light waves and absorbing the oranges, yellows, blues, greens, and violets. A blue bird looks blue because it is reflecting blue light waves and absorbing the others. The dirt looks brown because it is reflecting several light waves that together look brown, and absorbing other light waves.
Using Light Energy We use light energy every day to see. We use it in many other ways, too. The leaves of plants reflect green light waves and absorb others. The energy they absorb is used by the plants to make sugars through photosynthesis. These sugars feed the plants and the plants we eat give energy to us. All the energy we get to move and grow comes from plants. We can use the energy in light to make heat in many ways. We can color things black to absorb the light waves. We can use mirrors to reflect many light waves onto an object that absorbs them and turns them into heat. We can use this heat to warm houses and water or to cook food. We can also use light energy to make electricity. Solar cells can absorb light waves and turn the energy into electricity.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
21
Thermometer
Water Boils
ºF
ºC
Human Body
ºF
ºC
Water Freezes
ºF
ºC
You see lines across the thermometer to show three temperature readings. Read both scales of the thermometer and write the temperatures in the blank spaces on the lines. Now draw lines across the picture to show what you think the temperature is in the classroom, what you think the temperature is outside, and what you think the temperature is of the water in the drinking fountain. Use a thermometer to measure the actual temperatures of the classroom, outside, and the water in the fountain and draw lines across the picture to show those.
22
Light and Lighting
Solar Energy to Heat Objective To compare how different colors absorb energy from the sun. ? Question What is the relationship between absorbed solar energy and color? Prediction
Hypothesis Before going outdoors, predict which thermometer will be the hottest by numbering the thermometers on the right 1-3, with 1 as the hottest.
F
O 120
Materials
100 90
3 Thermometers Black paper White paper
80 70 60 50 40
Procedure
30 20
1. Put three thermometers in a sunny place.
10 0 -10
F
O
C
O
110
Result
50 40 30 20
120 110 100 90 80 70 60
10
50
0
30
-10 -20
C
O
40 20 10 0 -10
50 40 30
120 110 100 90 80
20
70
10
50
0 -10 -20
F
O
60
C
O
50 40 30 20 10
40
0
30 20 10 0 -10
-10 -20
2. Cover the bulb of one thermometer with black paper. Cover the bulb of one thermometer with white paper. Leave the bulb of the third thermometer uncovered. 3. Record your results by coloring the tubes of the thermometers to the right. 4. Look at the results and re-number the thermometers 1-3 with 1 as the hottest.
Conclusion 1. Which color absorbed the most energy? What evidence from the activity shows you this? 2. How should this information affect your clothing choices? What color will you wear on a sunny day? 3. Which will be hotter on a sunny day, a car with a dark interior, or a car with a light tan interior? How do you know?
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
23
Solar Balloon Objective To explore how light transforms to heat.
? Question What will happen when the solar balloon is filled with air and taken outside on a sunny day?
Hypothesis In your science notebook, write a prediction to answer the question above. Be sure to support your hypothesis using the concepts you explored in previous activity. Incorporate at least five words from the word bank in your explanation. Circle the words you chose to use!
Materials Solar balloon Fishing line or lightweight string Sunny day
Word Bank absorbs air converts gas heat light radiant energy reflection transforms thermal energy
Procedure 1. Take the solar balloon outside. Tie one end of the balloon and fill it with air. When the balloon is full, tie the open end closed. Tie fishing line or lightweight string to the balloon and let it sit in the sunlight. Observe what happens. Record your observations.
Conclusion 1. Explain what happened to the air inside the balloon and why it rose? 2. Will the balloon fly on a sunny but very cold winter day?
Extension 1. How might you get the balloon to fly on a cloudy day?
24
Light and Lighting
Radiometer Objective To explore how a radiometer works.
? Question How does a radiometer turn the sun’s energy into motion?
Hypothesis Examine the radiometer and predict which way the vanes will spin when it is placed in the sun. Color the PREDICTION ARROW that shows the direction you think the vanes will spin.
Procedure 1. Put the radiometer in bright sunlight and observe the radiometer’s vanes. 2. Record your results. Color the RESULT ARROW that shows the direction the vanes are spinning.
Conclusion 1. Explain how the radiometer turns the sun’s energy into motion.
Extension 1. Will the radiometer work in artificial light? 2. Will the vanes of the radiometer spin faster if the light is brighter?
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
25
Radiometer Explanation Top View of Radiometer
TOP VIEW OF RADIOMETER
radiant energy
radiant energy
enlarged
and
re b en oun er d gy
radiant energy
d oun reb rgy ene
radiant energy
When the radiometer is put in light, the vanes absorb energy. The light energy is changed into heat. The black side of the vane absorbs more of the light energy, and changes it to heat. This causes the air around the vanes to heat up. When the air molecules hit the black side, they bounce back with more energy than when they hit the white side. Since there is more of a push on one side than the other, the vanes begin to turn. The more light energy that reaches the radiometer, the more heat is produced, and the faster the vanes spin. If both sides of the vanes were the same color, the radiometer vanes would never move!
26
Light and Lighting
Lightsticks Background Some chemical reactions produce light. Lightsticks have two chemicals inside them. One of the chemicals is in the glass container inside the lightstick. If you bend the lightstick and break the glass container, the chemicals react and form a new chemical. The chemical reaction also produces light.
Objective To explore chemical reactions with light and heat.
?
Question
How does heat affect the light produced by a lightstick?
Hypothesis Read the procedure and make a prediction to answer the question.
Materials 2 Lightsticks Cup of ice water Cup of warm water
Procedure 1. Bend the lightsticks until the glass containers inside break, then shake to mix the chemicals. Observe the amount of light the lightsticks produce. 2. Place one lightstick in ice water and one in warm water. Observe any changes to the lightsticks.
Conclusion 1. Explain how heat affects the chemical reaction in a lightstick.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
27
NaturePrint® Paper Objective To explore chemical reactions with light and heat. ? Question How does sunlight affect the chemicals in different kinds of paper?
Hypothesis Predict how sunlight will affect NaturePrint® Paper.
Materials 1 Cut-out of the sun Sheet of NaturePrint® Paper Objects found outside or brought from home
Procedure 1. Cut out the sun picture on page 29. 2. Place the sun picture and your objects on the NaturePrint® Paper. 3. Place the piece of paper in direct sunlight. 4. After two minutes, pick up the NaturePrint® Paper and carefully carry it to the shade. 5. Remove the objects and sun picture and place the NaturePrint® Paper in water for one minute. 6. Allow the NaturePrint® Paper to dry. 7. Record what you see when looking at your dried NaturePrint® Paper on your observation chart.
28
Light and Lighting
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
29
30
Light and Lighting
Observations Make a diagram of your piece of dried NaturePrint® Paper below.
Side with Sun Cutout
Side with Objects You Chose
Conclusion 1. Describe how your NaturePrint® Paper changed over time. Explain why you think this occurred.
Extensions 1. Will a similar reaction occur with colored construction paper if left in the sun? 2. Will a similar reaction occur with colored cloth?
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
31
Glow Toys Background Glow toys are made of special material that stores energy from the light. The light “energizes” the material. When it’s placed in the dark, it will glow until the energized material releases all of its stored energy.
Objective To explore how light is stored and released in some objects.
?
Question
How does sunlight affect a glow toy?
Hypothesis Read the procedure and make a prediction to answer the question.
Materials 2 Glow toys Black construction paper Scissors Tape
Procedure 1. Make a pouch of black construction paper and put one of the glow toys inside. 2. For five minutes, put the pouch in the sun along with an uncovered glow toy. 3. Take the glow toy and the pouch into a darkened room. Observe the glow toy by itself. Look into the pouch and observe the other glow toy.
Conclusion 1. How does energy from the sun affect a glow toy?
Extension 1. Does artificial light affect a glow toy in the same way as sunlight? 2. How could glow toy technology be used to keep you safe?
32
Light and Lighting
Glow Toy Explanation How a Glow Toy Works
A glow toy stores radiant energy when it is left in the light. Photons of light hit electrons in the glow toy, causing them to jump to higher energy levels. When the electrons return to lower energy levels, they emit photons of light, causing the toy to glow. All glow-in-the-dark substances contain phosphors. A phosphor is a substance that radiates visible light after being energized. The two places where we most commonly see phosphors are in TV screens, computer monitors, and in fluorescent lights. In a TV screen, an electron beam strikes the phosphor to energize it. In a fluorescent light, ultraviolet light energizes the phosphor coating on the bulb. In both cases, what you see is visible light. A color TV screen actually contains thousands of tiny phosphor picture elements that emit three different colors (red, green, and blue). In the case of a fluorescent light, there is normally a mixture of phosphors that together create light that looks white to us. Thousands of chemical substances behave like phosphors. Phosphors have three characteristics: The type of energy they require to be energized The color of the visible light that they produce The length of time that they glow (known as the persistence of the phosphor) To make a glow-in-the-dark toy, a phosphor is used that is energized by normal light and has a very long persistence. The phosphor is mixed into a plastic and molded to make most glow toys, or even stickers for your ceiling!
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
33
UV Beads Background UV stands for Ultra Violet light, a type of radiation or energy that travels in a wave-like pattern. UV light is found within sunlight but is invisible. You are probably aware of the effects of UV radiation because you wear sunscreen and sunglasses to protect you from it. UV light produces chemical reactions that can cause a substance to glow or fluoresce, or your skin to burn or tan. It also causes the formation of Vitamin D, an essential vitamin for humans and other organisms. A good amount of harmful UV radiation gets blocked by the ozone layer, but the little amounts that get through will lead to these chemical changes. UV beads contain special color-changing pigments that are sensitive to UV light from the sun and other sources.
Objective To explore how light is stored and released in some objects. ? Question What will happen to the beads in the sun?
Hypothesis Predict how sunlight will affect the UV beads.
Materials 5 UV beads 1 Pipe cleaner
Procedure 1. String the UV beads on the pipe cleaner. Twist the pipe cleaner into a loosely-fitting bracelet and wear on your wrist. 2. Take your bracelet outside. Observe what happens to your beads. 3. Compare your bracelet to the teacher’s bag of beads with sunscreen.
Conclusion 1. What happened to your beads outside in the sun? 2. How does sunscreen affect the UV beads?
Extension 1. Will the beads do the same thing inside as they do in the sunlight? Why or why not?
34
Light and Lighting
How Light Travels Objective To investigate how light travels.
?
Question
Does light travel in a predictable way?
Hypothesis Read the procedure and make a prediction to answer the question.
Materials 1 Flashlight 2 Pieces of cardboard Sharp pencil Clay
Procedure 1. With a pencil, make a hole in the same place in each piece of cardboard. 2. Use the clay to hold the pieces of cardboard upright. Use the diagram below to set up the pieces of cardboard. 3. Shine the light from the flashlight through the holes in the cardboard. You might have to move one of the pieces of cardboard until you can shine the light through both holes and onto the wall. 4. Observe the path that the light travels from the flashlight to the wall.
Conclusion 1. How does light travel?
Extension 1. Look at the light bulb in the flashlight. Why do you think there is shiny metal behind the bulb? 2. Is it better to read with an overhead light or a desk light? Why?
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
35
Making Shadows Background Shadows are areas where light doesn’t reach. Explore the different shadows that a crayon makes when you move the light source.
Objective To investigate how shadows are created.
Materials Crayon Piece of clay Ruler Flashlight
Procedure 1. Place a crayon in a piece of clay so that it is standing straight up. 2. Move the flashlight at different distances from and angles to the crayon and observe the shadows, like in the pictures below.
Conclusion 1. What variables affect the size and shape of an object’s shadow?
36
Light and Lighting
Where is the Sun? Circle the location of the sun in each picture. You can circle more than one location.
1.
2.
Front Back
Front Back
Left Right
Left Right
High Low Overhead
High Low Overhead
3.
4.
Front Back
Front Back
Left Right
Left Right
High Low Overhead
High Low Overhead
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
37
Hand Shadows
38
Light and Lighting
Spectroscope Background A spectroscope separates visible light into individual colors of light, a lot like a prism. Drops of water can also act like a prism and separate light into the colors of a rainbow.
Objective To separate visible light into separate colors.
?
Question
What colors of light make up visible light?
Hypothesis What colors of light will you be able to see with the spectroscope.
Materials 1 Spectroscope Flashlight Colored pencils or crayons Spray bottle filled with water
Procedure 1. Look into the round circle end of the spectroscope, aiming it toward the flashlight or another bright light. Turn the spectroscope until you see a band of colors off to the side. 2. In the box below, draw the colors in the order you see them. 3. Go outside on a sunny day with the spray bottle filled with water. Spray the water into the air. Have the other students walk around until they see a rainbow in the spray of water.
Conclusion 1. What colors of light make up visible light? 2. Does a rainbow have the same colors in the same order as a spectroscope?
Extension 1. How would colored glasses change the colors you would see in the spectroscope?
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
39
Reflection Background When light hits a flat, shiny object like a mirror, it is reflected. It bounces off the object.
Objective To investigate the reflection of light.
?
Question
How does light behave when it is reflected from an object?
Hypothesis How do you think mirrors affect light?
Materials Mirror Flashlight Piece of yarn 2 Partners
Procedure 1. Place the mirror face up on the floor. Stand three feet from the mirror and shine the flashlight beam onto the mirror. Hold the flashlight at the eye level of your partner. 2. Have your partner stand on the other side of the mirror and move around until he/she finds the beam of reflected light. Observe the distance of your partner from the mirror. 3. Hold the flashlight at waist level. Have the partner move until he/she finds the beam. Observe the distance of your partner from the mirror. 4. Move back several feet and see if you and your partner can figure out where he/she should stand to see the beam of light. 5. Use a long piece of yarn to show the path of the light. Hold one end of the yarn to the end of the flashlight. Have someone stretch out the yarn straight to the mirror, then to your partner at eye level. 6. Observe the angles that the yarn makes from the ground.
Conclusion 1. How is light reflected? 2. How does the angle of the light traveling to the mirror compare to the angle of the reflected light?
40
Light and Lighting
Maze 1 Solve the maze of mirrors! Draw the reflected light wave as it is reflected from mirror to mirror until you reach the last mirror before the light wave leaves the page. This is the final mirror. HINTS: Every mirror is part of the maze. Focus on the middle of the mirrors.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
41
Maze 2 Solve the maze of mirrors! Draw the reflected light wave as it is reflected from mirror to mirror until you reach the last mirror before the light wave travels off the page. This is the final mirror. Every mirror is a part of the maze.
42
Light and Lighting
Solar House Background A photovoltaic (PV) cell changes radiant energy into electricity. Electricity can run a motor to make a fan move.
Objective To investigate a PV cell, and describe how it transforms energy.
?
Question
How can we use the sun’s energy to make electricity?
Materials PV cell kit Shoe box Scissors Sharp pencil
Procedure 1. Make a shoe box into a house with big windows and a door in the front. 2. Make a hole in the top of the box with the pencil. Place the PV cell on top of the house. 3. Put the stem of the motor through the hole. Push the hole in the fan onto the stem of the motor that is sticking through the ceiling. 4. On a sunny day, place the house in the sun. Observe the fan turn as the PV cell turns radiant energy from the sun into electricity and then into motion. 5. Tilt the PV cell at different angles to the sun and observe the speed of the turning fan.
Conclusion 1. How does the angle of the PV cell to the sun affect the amount of electricity it produces?
Extension 1. Make a list of ten ways you could use a PV cell at home.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
43
Photovoltaic Cells Explanation Step 1
When the two wafers are placed together, the free electrons from the n-layer are attracted to the p-layer. An interesting thing happens at the moment of contact between the two wafers--free electrons from the n-layer flow into the p-layer for a split second, then form a barrier to prevent more electrons from moving from one layer to the other. This contact point and barrier is called the p-n junction. Once the layers have been joined, there is a negative charge in the p-layer section of the junction and a positive charge in the n-layer section of the junction. This imbalance in the charge of the two layers at the p-n junction produces an electric field between the p-layer and the n-layer.
A location that can accept an electron Free electron Proton Tightly-held electron
STEP 1 NEGATIVE CHARACTER
n-type silicon p-type silicon
POSITIVE CHARACTER
electric field
STEP 2 POSITIVE CHARGE
STEP 4
n-type p-n junction p-type
NEGATIVE CHARGE
PHOTONS
STEP 3 electric field
Step 2
From Silicon to Electricity
electric field
Pure silicon is used to form very thin wafers. In some of these wafers, a small amount of the element phosphorous is added. In the other wafers, a small amount of the element boron is added. The phosphorous gives its wafer an excess of free electrons; therefore, this wafer will have a negative character. This wafer is called the n-layer. The n-layer is not a charged wafer--it has an equal number of protons and electrons--but some of the electrons are not held tightly to the atoms. They are free to move about. The boron gives its wafer a positive character, because it has a tendency to attract electrons. This layer also has an equal number of protons and electrons--it has a positive character but not a positive charge. This wafer is called the p-layer.
POSITIVE CHARGE
SUN n-type p-n junction p-type
NEGATIVE CHARGE
SUN sun
FREE ELECTRON
load
Step 3 If the PV cell is placed in the sun, photons of light energy strike the electrons in the p-n junction and energize them, knocking them free of their atoms. These electrons are attracted to the positive charge in the n-layer and are repelled by the negative charge in the p-layer.
Step 4 A wire can be attached from the p-layer to the n-layer. As the free electrons are pushed into the n-layer, they repel each other. The wire provides a path for the electrons to flow away from each other. This flow of electrons is an electric current.
44
Light and Lighting
Comparing Light Bulbs Objective To compare incandescent and compact fluorescent light bulbs to see which one produces more heat. An energy efficient light bulb should produce light, not heat!
?
Question
Does an incandescent or compact fluorescent light bulb produce more heat?
Hypothesis Read the procedure and make a prediction to answer the question.
Materials Lamp Incandescent bulb Compact fluorescent light bulb that produces similar lumens (the measure of the amount of light a bulb produces)
Procedure 1. Put the incandescent bulb into the lamp and turn it on. Observe the amount of light and heat that the bulb produces. Be very careful not to touch the bulb; it can get very hot. 2. Turn off the lamp and let the bulb cool. 3. Take the incandescent bulb out of the lamp and put in the compact fluorescent bulb. Turn on the lamp. Observe the amount of light and heat the bulb produces. *If you have two lamps, you can compare the bulbs at the same time.
Conclusion 1. Which bulb produced more light? More heat? 2. Which bulb do you think is more energy efficient? Explain why you think this, using your observations above.
Extensions 1. Examine the packaging of an incandescent and compact fluorescent bulb with similar lumen output. 2. Considering the cost of the bulb, the amount of energy it uses, and the number of hours it will last, calculate which bulb is the better buy.
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
45
Facts of Light We use a lot of energy to make light so that we can see. About 30 percent of the electricity used by your school is for lighting! Our homes use a lot of energy for lighting, too. About six percent of the energy used in your home is for lighting. Changing to energy efficient lighting is one of the quickest and easiest ways to decrease your electric bill. If your home uses inefficient incandescent bulbs—the same technology developed in 1879 by Thomas Edison—you are wasting a lot of energy and money. These bulbs are surprisingly inefficient, converting up to 90 percent of the electricity they consume into heat. The Energy Independence and Security Act of 2007 changed the standards for the efficiency of light bulbs used most often. By 2014, most general use bulbs will need to be 30 percent more efficient than traditional, inefficient incandescent bulbs. What do the new standards mean for consumers? The purpose of the new efficiency standards is to give people the same amount of light using less energy. Most incandescent light bulbs will be slowly phased out and no longer for sale. There are several lighting choices on the market that already meet the new efficiency standards. Energy-saving incandescent, or halogen, bulbs are different than traditional, inefficient incandescent bulbs because they have a capsule around the filament (the wire inside the bulb) filled with halogen gas. This allows the bulbs to last three times longer and use 25 percent less energy. Compact fluorescent lamps (CFLs) provide the same amount of light as incandescent bulbs but use 75 percent less energy and last ten times longer. CFLs produce very little heat. Using CFLs can help cut lighting costs up to 75 percent and reduces environmental impacts. Today’s CFL bulbs fit almost any socket, produce a warm glow and, unlike earlier models, no longer flicker and dim. CFLs have a small amount of mercury inside and should always be recycled rather than thrown away. Many retailers recycle CFLs for free. Light emitting diodes, better known as LEDs, are gaining in popularity. Once used mainly for exit signs and power on/off indicators, improved technology and lowering prices are enabling LEDs to be used in place of incandescents and CFLs. LEDs are one of the most energy-efficient lighting choices available today. LEDs use 75 percent less energy than traditional incandescents, and have an average lifespan of at least 25,000 hours. Today, LEDs are expensive, but they use even less energy than CFLs, saving more electricity and producing fewer carbon dioxide emissions. As the demand for LEDs increases, the cost will come down and become competitive with CFLs. The U.S. Department of Energy estimates that widespread adoption of LED lighting by 2027 would reduce lighting electricity demand by 33 percent. This would avoid construction of 40 new power plants.
46
INCANDESCENT BULB
HALOGEN
COMPACT FLUORESCENT (CFL)
LIGHT EMITTING DIODE (LED)
Brightness
850 lumens
850 lumens
850 lumens
850 lumens
Life of Bulb
1,000 hours
3,000 hours
10,000 hours
25,000 hours
Energy Used
60 watts = 0.06 kW
43 watts = 0.043 kW
13 watts = 0.013 kW
12 watts = 0.012 kW
Price per Bulb
$0.50
$3.00
$3.00
$40.00
Light and Lighting
Facts of Light The graphic on the previous page shows four light bulbs that produce the same amount of light. You might use bulbs like these as a bright overhead light. One bulb is an incandescent light bulb (IL), one is halogen, one is a compact fluorescent lamp (CFL), and another is a light emitting diode (LED). Which one is the better bargain? Let’s do the math and compare the four light bulbs using the residential cost of electricity at $0.12/ kWh. 1. Determine how many bulbs you will need to produce 25,000 hours of light by dividing 25,000 by the number of hours each bulb produces light. 2. Multiply the number of bulbs you will need to produce 25,000 hours of light by the price of each bulb. The cost of each bulb has been given to you. 3. Multiply the wattage of the bulbs (using the kW number given) by 25,000 hours to determine kilowatthours (kWh) consumed. 4. Multiply the number of kilowatt-hours by the cost per kilowatt-hour to determine the cost of electricity to produce 25,000 hours of light. 5. Add the cost of the bulbs plus the cost of electricity to determine the life cycle cost for each bulb. Which one is the better bargain? 6. Compare the environmental impact of using each type of bulb. Multiply the total kWh consumption by the average amount of carbon dioxide produced by a power plant. This will give you the pounds of carbon dioxide produced over the life of each bulb. Which one has the least environmental impact?
All bulbs provide about 850 lumens of light. COST OF BULB
INCANDESCENT BULB
HALOGEN
COMPACT FLUORESCENT (CFL)
LIGHT EMITTING DIODE (LED)
1,000 hours
3,000 hours
10,000 hours
25,000 hours
$0.50
$3.00
$3.00
$40.00
Cost of Electricity
INCANDESCENT BULB
LIGHT EMITTING DIODE (LED)
25,000 hours 60 watts = 0.060 kW
HALOGEN 25,000 hours
COMPACT FLUORESCENT (CFL)
Total Hours Wattage
43 watts = 0.043 kW
25,000 hours 13 watts = 0.013 kW
25,000 hours 12 watts = 0.012 kW
$0.12
$0.12
$0.12
$0.12
INCANDESCENT BULB
HALOGEN
COMPACT FLUORESCENT (CFL)
LIGHT EMITTING DIODE (LED)
1.6 lb/kWh
1.6 lb/kWh
1.6 lb/kWh
1.6 lb/kWh
Life of bulb (how long it will light)
Number of bulbs to get 25,000 hours
x Price per bulb = Cost of bulbs for 25,000 hours of light
x = Total kWh consumption x Price of electricity per kWh = Cost of Electricity Life Cycle Cost
Cost of bulbs
+ Cost of electricity = Life cycle cost Environmental Impact
x =
Total kWh consumption Pounds (lbs) of carbon dioxide per kWh Pounds of carbon dioxide produced
©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
47
Energy Used
Life of Bulb
Brightness
$0.50
60 watts = 0.06 kW
1,000 hours
850 lumens
INCANDESCENT BULB
$3.00
43 watts = 0.043 kW
3,000 hours
850 lumens
HALOGEN
$3.00
13 watts = 0.013 kW
10,000 hours
850 lumens
COMPACT FLUORESCENT (CFL)
$40.00
12 watts = 0.012 kW
25,000 hours
850 lumens
LIGHT EMITTING DIODE (LED)
Light Bulb Comparison
Price per Bulb
Light and Lighting
48
Home Energy Use Survey Be an Energy Detective Complete this survey to begin to understand how much energy is used in your home. If you are not sure about a question, ask an adult for help. 1. Number of incandescent light bulbs in your home. ______ 2. Number of compact fluorescent light bulbs in your home. ______ 3. Number of times your dishwasher is run per week. ______ 4. How often the Energy Saver feature on the dishwasher is used. 0%
25%
50%
75%
100%
5. Number of loads of laundry washed per week. ______ 6. Percentage of laundry loads washed and rinsed in cold water. 0%
25%
50%
75%
100%
7. Total number of baths taken by all family members each week. ______ 8. Total number of showers taken by all family members each week. ______ 9. Average length of each shower. _______ minutes 10. Water heater temperature is set at 120°F or lower. ______ 11. Water heater is wrapped in an insulated blanket. ______ 12. Thermostat settings: Cooling Season: Day ________°F Night ________°F Heating Season: Day ________°F Night ________°F 13. Fans are used instead of air conditioning in warm weather. ______ 14. Window blinds are closed on hot, sunny days and open on cold, sunny days. ______ 15. How many times a day: is a light left on in an unoccupied room? ______ is a TV, radio, computer, or video game left on with no one using it? ______ is the water allowed to run needlessly when brushing teeth or washing dishes? ______ is the stove or oven used to cook instead of the microwave or toaster oven? ______ is a door or window open when the heat or air conditioning is on? ______ ©2012 The NEED Project
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
49
Light and Lighting Survey 1. Circle the girl who would feel hotter.
2. Circle the boy who would have the longest shadow.
3. Light can be reflected or absorbed.
True
False
4. Some substances can store light.
True
False
5. A mirror absorbs light.
True
False
6. A PV cell turns light energy into heat.
True
False
7. Chemical reactions can produce light.
True
False
8. Circle the light bulb that is more energy efficient.
50
Light and Lighting
Light and Lighting Evaluation Form State: ___________ Grade Level: ___________ Number of Students: __________ 1. Did you conduct the entire unit?
Yes
No
2. Were the instructions clear and easy to follow?
Yes
No
3. Did the activities meet your academic objectives?
Yes
No
4. Were the activities age appropriate?
Yes
No
5. Were the allotted times sufficient to conduct the activities?
Yes
No
6. Were the activities easy to use?
Yes
No
7. Was the preparation required acceptable for the activities?
Yes
No
8. Were the students interested and motivated?
Yes
No
9. Was the energy knowledge content age appropriate?
Yes
No
10. Would you teach this unit again? Please explain any ‘no’ statement below.
Yes
No
How would you rate the unit overall?
excellent
good
fair
poor
How would your students rate the unit overall?
excellent
good
fair
poor
What would make the unit more useful to you?
Other Comments:
Please fax or mail to: The NEED Project
©2012 The NEED Project
P.O. Box 10101 Manassas, VA 20108 FAX: 1-800-847-1820
P.O. Box 10101, Manassas, VA 20108
1.800.875.5029
www.NEED.org
51
NEED National Sponsors and Partners American Association of Blacks in Energy Hydro Research Foundation American Chemistry Council Idaho Department of Education American Electric Power Idaho National Laboratory American Electric Power Foundation Illinois Clean Energy Community Foundation American Solar Energy Society Independent Petroleum Association of America American Wind Energy Association Independent Petroleum Association of Appalachian Regional Commission New Mexico Areva Indiana Michigan Power Arkansas Energy Office Interstate Renewable Energy Council Armstrong Energy Corporation iStem–Idaho STEM Education Association of Desk & Derrick Clubs Kansas City Power and Light Robert L. Bayless, Producer, LLC KBR BP Kentucky Clean Fuels Coalition BP Alaska Kentucky Department of Education C&E Operators Kentucky Department of Energy Cape and Islands Self Reliance Development and Independence Cape Cod Cooperative Extension Kentucky Oil and Gas Association Cape Light Compact–Massachusetts Kentucky Propane Education and Research Council L.J. and Wilma Carr Kentucky River Properties LLC Central Virginia Community College Kentucky Utilities Company Chevron Lenfest Foundation Chevron Energy Solutions Littler Mendelson ComEd Llano Land and Exploration ConEdison Solutions Los Alamos National Laboratory ConocoPhillips Louisville Gas and Electric Company Council on Foreign Relations Maine Energy Education Project CPS Energy Maine Public Service Company Dart Foundation Marianas Islands Energy Office David Petroleum Corporation Massachusetts Division of Energy Resources Desk and Derrick of Roswell, NM Lee Matherne Family Foundation Dominion Michigan Oil and Gas Producers Education Dominion Foundation Foundation DTE Energy Foundation Midwest Energy Cooperative Duke Energy Mississippi Development Authority–Energy East Kentucky Power Division El Paso Foundation Montana Energy Education Council E.M.G. Oil Properties The Mosaic Company Encana NADA Scientific Encana Cares Foundation NASA Energy Education for Michigan National Association of State Energy Officials Energy Training Solutions National Fuel Energy Solutions Foundation National Grid Entergy National Hydropower Association Equitable Resources National Ocean Industries Association First Roswell Company National Renewable Energy Laboratory Foundation for Environmental Education Nebraska Public Power District FPL New Mexico Oil Corporation The Franklin Institute New Mexico Landman’s Association GenOn Energy–California New Orleans Solar Schools Initiative Georgia Environmental Facilities Authority New York Power Authority Government of Thailand–Energy Ministry NSTAR Guam Energy Office OCI Enterprises Gulf Power Offshore Energy Center Halliburton Foundation Offshore Technology Conference Hawaii Energy Ohio Energy Project Gerald Harrington, Geologist Pacific Gas and Electric Company Houston Museum of Natural Science ©2012The TheNEED NEEDProject Project P.O. www.NEED.org ©2012 P.O.Box Box10101, 10101,Manassas, Manassas,VA VA20108 201081.800.875.5029 1.800.875.5029 www.NEED.org
PECO Petroleum Equipment Suppliers Association Phillips 66 PNM Puerto Rico Energy Affairs Administration Puget Sound Energy Rhode Island Office of Energy Resources RiverWorks Discovery Roswell Climate Change Committee Roswell Geological Society Sacramento Municipal Utility District Saudi Aramco Schneider Electric Science Museum of Virginia C.T. Seaver Trust Shell Snohomish County Public Utility District–WA Society of Petroleum Engineers SolarWorld USA David Sorenson Southern Company Southern LNG Southwest Gas Space Sciences Laboratory–University of California Berkeley Tennessee Department of Economic and Community Development–Energy Division Tennessee Valley Authority Toyota TXU Energy United States Energy Association University of Nevada–Las Vegas, NV U.S. Department of Energy U.S. Department of Energy–Hydrogen Program U.S. Department of Energy–Office of Energy Efficiency and Renewable Energy U.S. Department of Energy–Office of Fossil Energy U.S. Department of Energy–Wind for Schools U.S. Department of Energy–Wind Powering America U.S. Department of the Interior– Bureau of Land Management U.S. Department of the Interior–Bureau of Ocean Energy Management, Regulation and Enforcement U.S. Energy Information Administration U.S. Environmental Protection Agency Van Ness Feldman Virgin Islands Energy Office Virginia Department of Education Virginia Department of Mines, Minerals and Energy Walmart Foundation Washington and Lee University Western Kentucky Science Alliance W. Plack Carr Company Yates Petroleum Corporation
