One source of background radiation is cosmic rays. The cosmic rays that enter the Earth's atmosphere are known as primary cosmic rays. Most of these rays are fast-moving protons or fast-moving alpha-particles. Both the Earth's magnetic field and the Earth's atmosphere reduce the number of primary cosmic rays that reach the Earth's surface.

1. (a)(i)Name a source of background radiation apart from cosmic rays.[1]
2. (a)(ii)State one effect of background radiation.[1]
3. (a)(iii)State the number of protons and the number of neutrons in an alpha-particle.[2]
4. (a)(iv)Explain how the Earth's atmosphere reduces the number of alpha-particles that reach the surface.[1]
5. (a)(v)Fig. 11.1 shows an area where there is a uniform magnetic field into the page. On Fig. 11.1, draw a diagram to show the deflection of an alpha-particle by this magnetic field.[2]
6. (b)(i)Primary cosmic rays produce carbon-14 in the atmosphere. The half-life of carbon-14 is 5700 years. Define the term half-life.[2]
7. (b)(ii)A specimen of wood is found to contain 25000 atoms of carbon-14. An otherwise identical specimen taken from a living tree is found to contain 200000 atoms of carbon-14. Determine the age of the specimen that contains 25000 atoms of carbon-14.[2]
8. (b)(iii)State why it is not possible to use the amount of carbon-14 to date a specimen that is 570000 years old.[1]
9. (c)(i)Carbon-14 is one of the isotopes of carbon. Another isotope is carbon-12. Describe how a nucleus of carbon-14 differs from a nucleus of carbon-12.[2]
10. (c)(ii)Describe one similarity in the structure of the nuclei of these isotopes.[1]

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