1. The power source for the instrumentation on board the space probe is plutonium-238, which provides 470 W initially.

Plutonium-238 decays by α-particle emission with a half-life of 88 years. The kinetic energy of each α-particle is 8.8 × 10^–13 J.

i) Calculate the number N of plutonium-238 nuclei needed to provide the power of 470 W.

N = ......................................................... [3]

ii) Calculate the power P still available from the plutonium-238 source 100 years later.

P = ..................................................... W [3]