Question

Penetrating power of $\alpha $ -particle is:
A. More than $\gamma $ -rays
B. More than $\beta $ -rays
C. Less than $\beta $ -rays
D. None of these

Answer 1

Hint: Penetration power of a particle or radiation is defined as its power to pass through a substance. In general radioactive nuclides undergo decay to give alpha, beta, gamma, X-rays. All these rays have different energy, different characteristics and different penetration powers.

Complete Step by Step Solution:
$\alpha $ -rays consist of $\alpha $ particles. The alpha particles are actually helium atoms. Helium atoms have a mass number of $4$ and atomic number of $2$ . Alpha particles make stable nuclei. Due to high positive charge alpha particles are highly ionising and penetrate through a matter less effectively.

$\beta $ -rays consist of beta particles. The beta particles are actually high energetic electrons. Electrons are negatively charged particles of the nucleus that revolve around the nucleus. Due to its smaller size than alpha particles it has less ionising power and can penetrate through a matter.

$\gamma $ -rays are not material particles. It is a high energetic electromagnetic radiation consisting of a packet of energy. It is emitted due to radioactive decay of radioactive nuclide. Thus it has the highest penetrating power.

Thus penetrating power of $\alpha $ -particle is less than $\beta $ -rays.
Thus the correct option is C.

Note: The penetration power into a matter or nucleus is highest in case of gamma particles followed by beta and alpha particles or rays. Thus the order of penetration power is as follows: $\gamma >\beta >\alpha $ ray.