Which of the following radiations will have maximum penetration power?

The correct option is y -rays (Gamma rays).

To understand why gamma rays (γ-rays) have the maximum penetrating power among the given radiations, let us analyze the nature and characteristics of each type of radiation:

1. Alpha rays (α-rays):
Alpha particles consist of two protons and two neutrons, which is essentially a helium nucleus (with a +2 charge). Because of their relatively large mass and double positive charge, they interact strongly with matter and ionize atoms very easily. This high rate of ionization causes them to lose their energy very rapidly over a very short distance. Consequently, alpha particles have the lowest penetrating power and can be stopped by a single sheet of paper or even the outer layer of human skin.

2. Beta rays (β-rays):
Beta particles are high-energy, high-speed electrons or positrons (with a -1 or +1 charge). They are much lighter than alpha particles and carry less charge. Because of this, they are less ionizing than alpha particles and can travel farther into matter. However, they can still be easily stopped by a thin sheet of aluminum or plastic, representing moderate penetrating power.

3. X-rays:
X-rays are a form of high-energy electromagnetic radiation. Since they are photons (uncharged packet of energy) and have no mass, they do not interact as strongly with matter as charged particles (alpha and beta) do. This allows them to penetrate deeply into soft tissues, though they are absorbed by denser materials like bone or lead.

4. Gamma rays (γ-rays):
Gamma rays are also electromagnetic radiation (photons) like X-rays, but they generally have even shorter wavelengths, higher frequencies, and much higher energies. Because they are completely neutral (having zero charge) and have zero rest mass, they have a very low probability of interacting with atoms as they pass through matter. This extremely low ionization density allows them to travel great distances through air and pass through thick layers of materials. They require dense shielding, such as several inches of lead or feet of concrete, to be effectively stopped, giving them the maximum penetrating power among the options listed.