1. Match the definition with the following terms. 1. ionizing radiation

a) a positively charged particle (a Helium-4 nucleus) made up of two neutrons and two protons.

2. electromagnetic radiation

b) radiation that is capable of producing ions either directly or indirectly.

3. decay

c) the spontaneous decay of disintegration of an unstable atomic nucleus accompanied by the emission of radiation.

4. radioactivity

d) the change of one radioactive nuclide into a different nuclide by the spontaneous emission of alpha, beta, or gamma rays, or by electron capture.

5. nuclide

e) radiation consisting of electric and magnetic waves that travel at the speed of light.

6. beta particles

f) a highly penetrating type of nuclear radiation, similar to x-radiation, except that it comes from within the nucleus of an atom, and, in general, has a shorter wavelength.

7. gamma ray

g) any species of atom that exists for a measurable length of time; it can be distinguished by its atomic weight, atomic number, and energy state.

8. alpha particle

h) an electron of either positive charge (ß+) or negative charge (ß-), which has been emitted by an atomic nucleus or neutron in the process of a transformation.

2. Read the following text and fill in the missing words and word combinations.

ozone layer; skin cancer; in space without the protection; «radiation shield»; magnetic fields; higher energy particles; muons; black-hole accretion disks; luminous objects; cosmic microwave background radiation; many different types of radiation; outer space and the sun; our natural environment

Cosmic radiation is part of 1) ………….. , and we are constantly exposed to a certain amount of ionizing radiation. Radiation originating from 2) …………….. is called cosmic radiation and contributes about 13% of the background radiation level on Earth (a greater part is due to radon). Cosmic radiation is a collection of 3) ……………… from many different types of sources. When people speak simply of 'cosmic radiation' they are usually referring specifically to the 4) …………….. . This consists of very, very low energy photons (energy of about 2.78 Kelvin) whose spectrum is peaked in the microwave region and which are remnants from the time when the universe was only about 200,000 years old. There are also very old remnant neutrinos in the cosmic radiation. Neutrinos pass through just about everything with no effect so they are harmless. The photons are too low in energy to be dangerous. On top of these there are higher energy particles that are being created constantly by all 5) ………… in the universe. Photons of all different energies/wavelengths are being created by our sun, other stars, quasi-stellar objects, 6) ……….. , gamma-ray bursts and so on. These objects also produce high-energy massive particles such as electrons, 7) ………., protons and anti-protons. These 8) ……….. are potentially dangerous, but most of these particles never make it to the earth. They are deflected by 9) ………… between us and the source, or they interact with other particles, or they decay in flight. The particles that do make it to the earth interact with our atmosphere, which acts as a 10) ………….. . The high-energy cosmic rays bombard us all the time, but they interact quickly, producing particles of much lower energy which impact the earth harmlessly. If this was dangerous to us, we wouldn’t be here to discuss these things! Some particles, like neutrinos and high energy muons, are passing through us all the time, but they interact so weakly that they have no effect on our

bodies. Of course, if we were 11) …………. of our atmosphere then we would need some other type of shielding from the radiation (spacesuits and protective covering on our spacecrafts). The radiation to worry about, of course, is the «cosmic» radiation produced by our sun. There is only one type of cosmic radiation known to adversely affect us and that’s UV radiation from our sun, which causes 12) ………. in millions of people every year. Again, our atmosphere serves as a shield, but ultraviolet photons do make it through – and without that 3а3tecttive 13) ………. which blocks these photons we’re all going to need a lot more sunscreen!

3. Choose the correct answer. 1. Who is given credit for the discovery of X-ray? a) Henri Becquerel b) Wilhelm Roentgen c) Marie Curie d) Pierre Curie 2. After traveling through two half-value layers, the incident radiation has been reduced to a) 50% b) 35% c) 20 % d) None of the above 3. Who is given credit for the discovery of radioactive materials? a) Henri Becquerel b) Wilhelm Roentgen c) Marie Curie d) Pierre Curie 4. Stationary lab or shop X-ray systems usually rely on what to limit exposure to the radiation? a) Distance controls b) Time limits c) Shielding c) All of the above 5. X-rays and Gamma rays are a form of a) Light b) Particle radiation

c) Electromagnetic radiation d) Both B and C 6. X-rays and Gamma rays have significant penetrating power due to their a) Short wavelength b) Medium wavelength c) Long wavelength d) Wide range of wavelengths 7. A specific radioactive source will always produce gamma rays at the same a) Intensity b) Activity c) Energy levels d) None of the above 8. Ionizing radiation can be used in industrial radiography because the health hazards a) Have been eliminated with controls and procedures b) Are minimized through controls and procedures c) Are worth the risk d) Are being ignored 9. Higher energy radiation will have more a) Speed b) Incident intensity c) Penetrating power d) Both B and C 10. Radiographic contrast describe a) The sharpness of lines in a radiograph b) The differences in photographic density in a radiograph c) The average photographic density in a radiograph d) The difference in density between two different radiographs 11. There are four types of radiation-matter interactions that can contribute to the total attenuation. These are a) Compton scattering, pair production, photoelectric absorption, rayleigh scattering b) Compton scattering, electron exchange, photoelectric absorption, rayleigh scattering c) Electron exchange, pair production, photoelectric absorption, rayleigh scattering d) None of the above 12. X-rays and Gamma rays are often referred to as photons because a) They possess a charge

b) They have mass c) They occur as small packets of energy d) None of the above 13. Which of the following does not affect radiographic contrast? a) Attenuation differences in the component being inspected b) The wavelength of the radiation used c) The amount of scattered radiation d) The level of current used for the exposure 14. In comparison with lower-voltage radiographs, high voltage radiographic images have a) Less contrast sensitivity b) Greater contrast sensitivity c) Greater amounts of scatter radiation relative to primary beam intensity d) Less latitude 15. Film contrast is determined by a) The type of film used b) The process by which the film was developed c) The radiation energy used d) Both A and B 16. Which two types of radiation-matter interactions account for the majority of attenuation in typical industrial radiography? a) Compton scattering and photoelectric absorption b) Compton scattering and pair production c) Pair production and photoelectric absorption d) None of the above 17. A radiograph made with an exposure of 8mAm produces a density of 1.8. The sensitometric curve shows a difference in relative exposure between a density of 1.8 and the target density of 2.5 is 4. What must the new exposure time be to produce a radiograph with a density of 2.5? a) 4 mAminutes b) 2 mAminutes c) 32 mAminutes d) None of the above 18. When using geometric magnification to produce a radiograph, the penumbra will be reduced by a) A longer exposure b) A faster film speed c) A smaller source spot size

d) More X-ray energy 19. When flaws are in unknown locations, radiography is best suited for the detection of a) Volumetric defects such as porosity b) Tight linear defects such as cracks c) Material delaminations d) The flaw type does not matter

20. X-rays and Gamma rays present a health risk because they are a form of ionizing radiation, which means that the radiation has enough energy to a) Vibrate water molecules and generate heat b) Break chemical bonds c) Break physical bonds d) None of the above