GCSE Physics, Unit 5, Lesson 2 of 6

Alpha, beta and gamma radiation

GCSE Physics, Atomic structure and radioactivity, 20 minutes

Sign in

Why some nuclei are unstable, what alpha, beta, gamma and neutron radiation are, how far each travels and how strongly each ionises.

What you will learn

  • Describe what alpha, beta and gamma radiation are
  • Compare their penetration, range in air and ionising power
  • Identify the radiation from a source using absorber readings
  • Calculate a count rate and correct it for background

Unstable nuclei

Some nuclei are unstable.

To become more stable they give out radiation: this is radioactive decay. It is random: there is no way to say which nucleus will decay next, or when. Nothing you do to a nucleus, such as heating it or shaking it, changes when it decays.

  • Activity is the rate at which nuclei in a source decay, measured in becquerels: 1 Bq is one decay per second.
  • A Geiger-Muller tube and counter measure the count rate: the number of decays it detects each second or minute.
  • Radiation is always around us from rocks, the air and space: the background count. Subtract it before using a reading. A detector only catches some of the radiation, so the count rate it measures is less than the activity of the source.
  1. A tube records 1500 counts in 5 minutes; background is 0.4 counts per second
  2. 5 minutes = 300 s, so count rate = 1500 ÷ 300 = 5 counts per second
  3. corrected count rate = 5 − 0.4 = 4.6 counts per second

The rest of this lesson and its 9 practice questions are locked.

In this lesson

  1. Unstable nuclei
  2. Four kinds of nuclear radiation
  3. Which radiation is it?
  4. Try it: Watch decay happen at random
  5. Try it: Name the radiation

9 practice questions, marked as you go; about 20 minutes in all.

Key terms

Unstable, Radioactive decay, Activity, Background, Ionising, Most, Least

In this unit: Atomic structure and radioactivity

The nuclear atom and how its model developed, isotopes, alpha, beta and gamma radiation, nuclear equations, half-life, the hazards and uses of radiation, and fission and fusion.

All of Atomic structure and radioactivity

Back to the unit