Cambridge O Level Physics · Syllabus 5054 · Nuclear Physics
Radioactivity
What is Radioactivity?
Radioactivity is the spontaneous and random emission of alpha particles, beta particles and/or gamma radiation from unstable nuclei.
This definition is part of the Nuclear Physics chapter in Cambridge O Level Physics.
Questions students ask about Radioactivity
How do you calculate the corrected count rate when measuring radioactivity?
A Geiger–Müller tube and counter also registers background radiation — the ionising radiation always present, from radon gas in the air, rocks and buildings, food and drink, and cosmic rays. To find the count rate due to the source alone, measure the background count rate with the source removed, then subtract: corrected count rate = measured count rate − background count rate, with both rates in the same time unit.
Last reviewed Syllabus 2026-2028