Solved Sample Paper 4 — Question 14

(a) Background radiations are the radioactive radiations (such as α, β and γ) to which we all are exposed, even in the absence of an actual visible radioactive source. For example, radioactive substances such as potassium (K-40), carbon (C-14) and radium are present inside our body. Cosmic rays also contribute to background radiations.

(b) When a radioactive uranium nucleus $^{238}_{92}\text{U}$ emits an α particle, a new nucleus thorium $^{234}_{90}\text{Th}$ is formed and the change is represented as follows —

$_{92}^{238}\text{U} \longrightarrow \space _{90}^{234}\text{Th} + \space _{2}^{4}\text{He}$

(c) The rate of radioactive decay generally depends on the specific properties of the radioactive substance and is not directly proportional to temperature changes. Hence, increasing the temperature will not affect the rate of radioactivity.