Which radiation type is described as able to travel long distances and penetrate materials, requiring shielding with heavy lead?

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

Answer: (C)

The statement describes radiation that moves through air and other materials with little loss and requires dense shielding to reduce it. Gamma radiation fits this perfectly: it is electromagnetic radiation with no mass or charge, so it penetrates deeply and travels long distances before being attenuated. To shield against gamma rays, you need dense materials like lead, often in substantial thickness, to absorb the photons and lower the dose. By comparison, alpha particles are heavy and stop quickly in a sheet of paper or skin, beta particles are more penetrating than alpha but still can be halted by a few millimeters of material like aluminum, and neutrons require hydrogen-rich or specially designed shielding. Thus, gamma radiation is the one described.