Waves Properties of Waves ●Waves transfer energy. ●Waves may be either transverse or longitudinal. Candidates should understand that in a transverse wave the oscillations are perpendicular to the direction of energy transfer. In a longitudinal wave the oscillations are parallel to the direction of energy transfer. ●Electromagnetic waves are transverse, sound waves are longitudinal and mechanical waves may be either transverse or longitudinal. ●Longitudinal waves show areas of compression and rarefaction. ●The terms frequency, wavelength and amplitude. ●All waves obey the wave equation: v = f x λ v is speed in metres per second, m/s f is frequency in hertz, Hz λ is wavelength in metres, m Candidates are not required to recall the value of the speed of electromagnetic waves through a vacuum. Refraction ●The normal is a construction line perpendicular to the reflecting surface at the point of incidence. ●Waves undergo a change of direction when they are refracted at an interface. Waves are not refracted if travelling along the normal. Snell’s law and the reason why waves are refracted are not required. Reflection ●The angle of incidence is equal to the angle of reflection. ●The image produced in a plane mirror is virtual. Candidates will be expected to be able to construct ray diagrams. Diffraction ●Waves can be reflected, refracted and diffracted. Candidates should appreciate that significant diffraction only occurs when the wavelength of the wave is of the same order of magnitude as the size of the gap or obstacle. Sound ●Sound waves are longitudinal waves and cause vibrations in a medium, which are detected as sound. Sound is limited to human hearing and no details of the structure of the ear are required. ●The pitch of a sound is determined by its frequency and loudness by its amplitude. ●Echoes are reflections of sounds.

Properties of Waves All waves transfer ______________________________________________ Waves are created by ______________________________________________________________________________________ There are two types of waves; transverse and longitudinal. In a transverse wave the oscillations are _______________________________________ to the direction that the wave travels in. In a longitudinal wave the oscillations are _______________________________________ to the direction that the wave travels in. Examples of transverse waves are ____________________________________________________________________________ ________________________________________________________________________________________________________ Examples of longitudinal waves are ___________________________________________________________________________ ________________________________________________________________________________________________________ The diagram below is an example of a ____________________________________________ wave.

The diagram below is an example of a ____________________________________________ wave.

What do the following terms mean? Add them to the appropriate diagram above (if possible). Peak ___________________________________________________________________________________________________ Trough __________________________________________________________________________________________________ Compression _____________________________________________________________________________________________ Rarefaction ______________________________________________________________________________________________ Wavelength ______________________________________________________________________________________________ Amplitude _______________________________________________________________________________________________ Frequency _______________________________________________________________________________________________ Wave speed _____________________________________________________________________________________________

𝑣 = 𝑓×𝜆 Symbol

Quantity

Units

Unit Symbol

v f λ Rearrange the equation to make f and then λ the subject. Complete this table by calculating the missing values.

v

f 3 8

336 40 340 300 000 000

λ 1.2 0.015 0.8 0.8

850 500 000 000

The diagram shows waves being produced on a rope. The waves are not reflected by the wall. Draw an arrow on the diagram to show the direction in which the waves transfer energy. Which of the labelled arrows show the: Amplitude?

__________

Wavelength?

__________

State which type of wave is shown in the diagram and explain how you can tell? ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ The diagram shows two ways in which a wave can travel along a slinky spring. Clearly indicate and label the wavelength of Wave A and Wave B Which a longitudinal wave?

_______

Which is a transverse wave? _______

Refraction Explain what the word refraction means. ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ A student investigated the refraction of light as it passed out of a clear plastic block into the air. The diagram shows the apparatus the student used. What name is given to the dashed line? ____________________________ The angle i is the ______________________________________________ Use the letter r to mark the angle of refraction on the diagram. Which piece of equipment would you use to measure the angles? ____________________________________________________________ Why doesn’t the light ray bend when it enters the plastic block? ____________________________________________________________ Why does the light ray bend when it travels from the plastic block to the air? ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ The two diagrams, A and B, show a light ray travelling into a glass block. Complete the diagrams to show the paths that the light rays take as they enter and then leave the glass block.

In diagram A, when the light ray travels from air to glass it will bend _________________________________________ the normal. In diagram A, when the light ray travels from glass to air it will bend _________________________________________ the normal.

Reflection When dealing with light and mirrors it is important to use the correct vocabulary. Explain what the following words mean when used to describe an image produced through a lens. Inverted _________________________________________ Upright _________________________________________________ Magnified ________________________________________ Diminished ______________________________________________ Real ____________________________________________ Virtual __________________________________________________ The diagram shows a ray of light from a ray box that is reflected by a plane mirror. What name is given to the dashed line labelled as J? _________________________________________________________ What is the name given to K? _________________________________________________________ What is the name given to L? _________________________________________________________ If K was doubled what would happen to L? ________________________________________________________ If K was halved what would happen to L? ________________________________________________________ A student looking into the mirror can see an image of the ray box. Which words from the list at the top of this page can be used to describe the image that the student sees? ________________________________________________________________________________________________________ What is the law of reflection? ________________________________________________________________________________________________________ The diagram shows a model used to demonstrate an illusion known as ‘Pepper’s Ghost’. A small light bulb and thin sheet of glass are put inside a box. The thin sheet of glass acts as a mirror. Although the light bulb is switched on, a student looking into the box cannot see the bulb. What the student does see is a virtual image of the bulb.

Use a ruler to complete a ray diagram to show how the image of the light bulb is formed. Mark and label the position of the image. The image seen by the student is virtual. Why? ________________________________________________________________________________________________________

Diffraction Explain what the word diffraction means. ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ The diagrams show water waves in a ripple tank moving towards a gap in a barrier. The water waves diffract as they pass through the gap. Complete the diagrams to show the diffracted water waves.

Diffraction happens the most when the wavelength of the wave is ____________________________________________________ ________________________________________________________________________________________________________ Terrestrial television does not use satellites. Terrestrial television signals and radio signals both use radio waves. Radio signals are transmitted at a longer wavelength than terrestrial television signals.

In hilly areas it may be possible to receive radio signals but not receive terrestrial television signals. Explain why. ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________

Sound How are sounds produced? ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ How do drums produce sound? _____________________________________________________________________________ How to guitars produce sound? _____________________________________________________________________________ How do flutes produce sound?

_____________________________________________________________________________

Sound waves are longitudinal waves; use the diagram of a longitudinal wave to explain how sound waves travel from a speaker to an ear.

________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ What is a vacuum? ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ Explain why sound waves cannot travel through a vacuum. ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ The diagram shows the apparatus a teacher uses to demonstrate that sound can be reflected.

Using a ruler, draw on the diagram to show how sound from the loudspeaker is reflected by the sheet of metal to the sound sensor. What is the name given to the reflection of a sound? ______________________________________________________________ The teacher replaced the sheet of metal with a sheet of glass. When he did this, the reading on the sound level meter went down. Suggest why. ________________________________________________________________________________________________________ ________________________________________________________________________________________________________

The amplitude of a wave determines the ___________________________________________ of a wave. The frequency of a wave determines the ___________________________________________ of a wave. If a microphone is connected to an oscilloscope it will display the waveforms of different sounds like in the diagrams below

Which of the waveforms has the largest amplitude? _______

Which of the waveforms has the smallest amplitude? _______

Which of the waveforms has the highest frequency? _______

Which of the waveforms has the lowest frequency? _______

How would the sound that made waveform B be like compared to the sound that made waveform D? ________________________________________________________________________________________________________ How would the sound that made waveform C be like compared to the sound that made waveform A? ________________________________________________________________________________________________________ The diagrams show oscilloscope traces for the same musical note played on two different instruments. The oscilloscope settings are not changed.

How can you tell, from the diagrams, that it is the same musical note? ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ How can you tell, from the diagrams, that the musical note has been played on different instruments? ________________________________________________________________________________________________________ ________________________________________________________________________________________________________

The EM Spectrum All electromagnetic waves transfer energy but do not transfer ________________________________________ Complete the table by writing the initials of the waves of the EM spectrum and colours of the visible section into the correct boxes. Visible Light

X

G

R

Y

As we go from left to right in the table above the wavelength of the waves ___________________________________________ As we go from left to right in the table above the frequency of the waves

___________________________________________

As we go from left to right in the table above the energy of the waves

___________________________________________

As we go from left to right in the table above the speed of the waves

___________________________________________

Circle the correct values for the range of wavelengths of the electromagnetic spectrum.

The longest EM wavelength is around

1015m

104m

10m

The shortest EM wavelength is around

10-6 m

106m

10m

10-4m

10-15m

Complete this table by calculating the missing values. Give your answers to 2 decimal place.

EM Wave

Frequency (Hz)

Infrared

3.2 x 1013

Radio Waves

2.5 x 102

Microwaves Use Sending a text from a mobile phone Taking a photograph of a tree Killing cancerous cells inside a patient Turning off a television with a remote control Broadcasting a movie by satellite In sunbeds to give a sun tan Taking a thermal photograph of a human

Wavelength (m)

1.8 x 109 EM Wave

Use To sterilise surgical equipment A medical tracer injected into a patient Security ink used to mark your property Producing shadow images of bones Broadcasting a local radio show Turning a piece of bread into toast Cooking food in a microwave oven

EM Wave

What are the possible risks involved to human health in using a mobile phone? ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________