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The Nucleus and Radioactive Decay

Alpha, beta and gamma radiation: nature, penetration and range

  • 3 things to know
  • Unit A2 1

Overview

Nature of an alpha particle, nature of a beta-minus particle and nature of gamma radiation.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

How does each of the three radiations behave in a magnetic field?

Key term

Compare the ionising powers of alpha, beta and gamma radiation.

Key term

State the nature of gamma radiation.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State the nature of an alpha particle.

    Model answer

    An alpha particle is a helium nucleus, consisting of two protons and two neutrons, with a charge of +2e and a mass of about 4u.

  2. 2

    State the nature of a beta-minus particle.

    Model answer

    A beta-minus particle is a fast-moving electron emitted from the nucleus when a neutron changes into a proton, with a charge of −e and the mass of an electron.

  3. 3

    State the nature of gamma radiation.

    Model answer

    Gamma radiation is a very high-energy electromagnetic wave, or photon, emitted from a nucleus, with no charge and no mass.

  4. 4

    State the absorber needed to stop alpha radiation and its approximate range in air.

    Model answer

    Alpha radiation is stopped by a sheet of paper or a few centimetres of air, with a range in air of about 3 to 5 cm.

  5. 5

    State the absorber needed to stop beta radiation and its approximate range in air.

    Model answer

    Beta radiation is stopped by a few millimetres of aluminium and has a range in air of about a metre.

  6. 6

    Describe the absorption of gamma radiation.

    Model answer

    Gamma radiation is never completely stopped; its intensity is reduced to a small fraction by several centimetres of lead or by a thick concrete wall, and it falls off with distance in air according to an inverse square law.

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