Which type of radiation is the most dangerous due to penetrating power?

• A. Alpha
• B. Beta
• C. Neutron
• D. Gamma

Answer: (D)

The key idea is how far different types of radiation can travel through matter, which determines how hard it is to shield from them and how they affect the body. Among the common types listed, gamma radiation has the greatest penetrating power. Its photons have no charge and no mass, so they pass through skin, most clothing, and even several centimeters of concrete or lead before being absorbed. That deep reach means external exposure can affect internal organs, and shielding needs to be very dense and substantial.

Alpha particles are heavy and strongly ionizing, but they can be stopped by a sheet of paper or even a few centimeters of air, so they don’t penetrate far. Beta particles can pass through the outer skin but are stopped by a thin sheet of metal or plastic. Neutrons can be quite penetrating and can pass through many materials, but their shielding depends on material with suitable properties (often hydrogen-rich material). Gamma rays, however, remain the most penetrating among these, making them the most dangerous when the concern is how far radiation can travel and reach sensitive tissues.