Physics · GCSE · Atoms & Radioactivity

Radioactive decay, activity and count-rate

Radioactive decay, activity and count-rateFree2:47Heddy Score 3 of 7, below the standard
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What you need to know

  • Some isotopes have unstable nuclei, which give out radiation to become more stable; this is radioactive decay.
  • Radioactive decay is random, so we cannot predict when a particular nucleus will decay.
  • Activity is the rate at which a source decays, measured in becquerels (1 Bq is one decay per second).
  • Count-rate is the number of decays a detector such as a Geiger-Muller tube records each second, which is not the same as activity.
  • The four types of radiation are alpha particles, beta particles, gamma rays and neutrons.

In this clip

Runs 2:47, from 0:26 to 3:13 of the full video.

Heddy Score3/7, Below the standard
See the seven stars
  • Trusted source · passed. The creator's own upload, live and playable here.
  • On the map · not judged yet. A teacher watched it: it mainly teaches this map topic.
  • Spec-true · not judged yet. Accurate, and right for the current UK specification.
  • Focused · passed. One idea, short enough to watch in one go.
  • Accessible · passed. Good captions, clear sound and pictures.
  • Safe for children · not judged yet. Right for 11 to 16 year olds, with no sales pitch.
  • Proven · not judged yet. Earned from our students: they learn from it, find it helpful and watch it to the end.
★ passed · ☆ pending · ✕ failed
Our students

Not enough students yet

Our own students' answers. These are what move ★7 Proven.
On YouTube

859K views · 10.3K likes · Freesciencelessons 995K subscribers

As reported by YouTube on 2026-11-01. Not part of the Heddy Score.
How the Heddy Score works

Why we picked it

A concise GCSE explanation of activity, becquerels and count-rate alongside the types of nuclear radiation.

Freesciencelessons on YouTubechecked 2026-10-22

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