GENERAL KNOWLEDGE

Detailed explanation-1: -Alpha particles can easily be shielded by a single sheet of paper and cannot penetrate the outer dead layer of skin, so they pose no danger when their source is outside the human body.

Detailed explanation-2: -Alpha particles can be stopped completely by a sheet of paper. Beta particles travel appreciable distances in air, but can be reduced or stopped by a layer of clothing, thin sheet of plastic or a thin sheet of aluminum foil.

Detailed explanation-3: -Beta radiation can penetrate air and paper. It can be stopped by a thin sheet of aluminium.

Detailed explanation-4: -Gamma rays are a radiation hazard for the entire body. They can easily penetrate barriers that can stop alpha and beta particles, such as skin and clothing. Gamma rays have so much penetrating power that several inches of a dense material like lead, or even a few feet of concrete may be required to stop them.

Detailed explanation-5: -An alpha-particle is identical to the nucleus of a normal (atomic mass four) helium atom i.e. a doubly ionised helium atom. Alpha particles (also termed alpha radiation or alpha rays) was the first nuclear radiation to be discovered, beta particles and gamma rays were identified soon after.