11 A highly radioactive source that emits beta-particles is placed a few centimetres away from a detector, as shown in Fig. 11.1. [Figure 11.1]

1. (a)State the name of the particle which has the same mass and charge as a beta-particle.[1]
2. (b)State and explain why the metal casing in Fig. 11.1 is used.[2]
3. (c)(i)State and explain what happens to the number of particles detected in a minute as the radioactive source is moved: a few centimetres further away from the source[2]
4. (c)(ii)State and explain what happens to the number of particles detected in a minute as the radioactive source is moved: more than a metre away from the source.[2]
5. (d)A nucleus of strontium-90 (Sr-90) decays by beta emission to a nucleus of yttrium (Y). Complete the decay equation for this decay. ⁹⁰₃₈Sr → Y + ₋₁⁰β[3]
6. (e)(i)Describe how the process of nuclear fusion differs from the process of nuclear fission.[3]
7. (e)(ii)Describe the conditions needed for nuclear fusion to take place.[2]

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