A smoke detector contains a small radioactive source of americium-241. The source emits alpha-particles. [The question asks the user to draw a diagram in a blank space.] [The question also includes a blank table for comparing ionising effects and penetrating powers, with rows for "ionising effects" and "penetration effects".]

1. (a)(i)In the space below, draw a diagram of an apparatus that can be used to show that the source emits alpha-particles.[2]
2. (a)(ii)Describe how this apparatus is used.[2]
3. (a)(iii)Explain how the results of the test show that the source emits alpha-particles.[2]
4. (b)The smoke detector works because alpha-particles from the source ionise the air. Compare the relative ionising effects and penetrating powers of alpha-particles, beta-particles and gamma rays. ionising effects ................................................................................................................................................... penetration effects ................................................................................................................................................. [2][2]
5. (c)(i)Americium-241 has a half-life of 430 years. Radium-224 is another element that emits alpha-particles. It has a half-life of 3.6 days. Explain why americium-241 is more suitable as the radioactive source in a smoke detector than radium-224.[1]
6. (c)(ii)A smoke detector contains 8.0 × 10¹¹ atoms of americium-241. Calculate the time taken for the number of atoms of americium-241 to fall to 1.0 × 10¹¹. time = .....................................................[3][3]
7. (d)(i)When used correctly, the radioactive source in the smoke detector is less harmful than background radiation. State one harmful effect of background radiation.[1]
8. (d)(ii)A radioactive source is picked up using a long-handled tool. Explain why this is safer than using a short-handled tool.[2]