What is background radiation?

• A. A type of radiation only from medical imaging.
• B. Radiation produced by a laboratory experiment.
• C. Radiation that everyone receives from natural and manmade sources.
• D. A measure of the energy of a single photon.

Answer: (C)

Background radiation is the everyday level of ionizing radiation present in the environment that people are exposed to all the time. It comes from natural sources—cosmic rays from space, radioactive materials in soil, rocks, and building materials, and radon gas in homes—and from man-made sources such as medical imaging, industrial activities, and past nuclear fallout. Because it includes both natural and human-made origins, everyone receives this baseline exposure regardless of location or activities. It’s not about the energy of a single photon, and it’s not limited to one source of radiation; it’s the combined background exposure from multiple sources.