What are alpha, beta and gamma radiation?

• A. They are all forms of visible light.
• B. They are all electrons emitted from a nucleus.
• C. They are forms of sound waves.
• D. Types of ionising radiation with different properties and penetration abilities.

Answer: (D)

Alpha, beta and gamma radiation are types of ionising radiation released when unstable atomic nuclei decay. An alpha particle is a heavy helium nucleus, highly charged, so it ionises strongly but travels only a short distance and is stopped by a sheet of paper or skin. A beta particle is a fast electron (or positron): lighter and less ionising than an alpha particle but more penetrating, typically stopped by thin metal or plastic. Gamma radiation is high-energy electromagnetic radiation with no mass or charge, so it penetrates deeply and requires dense shielding such as lead or thick concrete. The common thread is that all three can ionise matter, but they differ in what they are (particle or photon) and how far they travel through materials, giving them different penetration abilities.