WAEC Physics 2012 Paper

Concept:Penetrating power of nuclear radiations depends on their energy and ability to pass through matter.Explanation:The increasing order of penetrating power is $\alpha < \beta < \gamma$.Alpha ($\alpha$) particles can be stopped by paper or skin.Beta ($\beta$) particles need a few millimetres of aluminium to stop them.Gamma ($\gamma$) rays are the most penetrating and require thick lead or concrete to be absorbed.Therefore, the order of decreasing penetrating power is $\gamma > \beta > \alpha$.Answer:The correct arrangement is $\gamma, \beta, \alpha$, which is option C.