Radioactivity Practice Test Answers
1. B and C
2. D
3. A
4. C
5. D
6. A
7. C
8. B
9. A
10. D
11. B
12. B
13. B
14. C
15. C
16. Geiger counter is a tube of gas with a wire running through the middle. When radiation comes through, it ionizes the air, turning the atoms into positively charged ions. These positive charges want their electrons back, so they attract the electrons in the metal, causing them to flow through the wire. This is electricity, and is amplified by an amplifier to produce a click. So the geiger counter makes a click every time it is exposed to radiation.
17. Fission reactions are used in nuclear plants to make electricity. The energy released by these reactions is used to heat water, turning it into steam. The steam is piped to a turbine, causing it to spin. This turns a generator which produces electricity. The water is condensed and recycled back to the reactor in order to be heated again.
18. Chain reaction in a power plant is controlled, and the chain reaction in a bomb is not. In a power plant boron, a material that absorbs neutrons, is used to slow the reaction. Because neutrons start fission events by running into large unstable atoms, the fewer neutrons there are, the less fission can occur. In a bomb, there is no boron, so each fission event starts two or more other fission events, leading to an uncontrolled chain reaction.
19. a) 84Po218 –> 2He4 + 82Pb214
b) 83Bi214 –> -1e0 + 84Po214
c) 6C14 –> +1e0 + 5B14
d) 5B9 + -1e0 –> 4Be9
20. They both result in the loss of one proton and no change in mass. In positron emission this happens when a proton spontaneously loses its positive charge in the form of a positron and thus becomes a neutron. In electron capture this happens when an electron collides with the nucleus, neutralizing a proton, causing it to become a neutron.
21. 5 halflives — 5 * 5730 = 28, 650 years
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