Question

which of the following have least penetrating power? and why ??

(a) alpha particles (b) gamma rays (c) beta particles (d) all have the same penetrating power.

Answer 1

Out of the following the penetration power of aplha particle will be the least as it is the weakest. It can be stopped even by a piece of paper. However beta particles move faster than the alpha particle and carry less charge(one electron compared to the 2 protons of an alpha particle)so it needs atleast few mm of aluminium to be stopped.
Of all the three gamma particle are the most penetrating one as they are high energetic waves and require many cms of lead to be stopped.

Order of penetrating power:-
$\alpha$ < $\beta$ < $\gamma$