National 5PhysicsSQARevision NotesRadiationNuclear RadiationAlpha, Beta & Gamma Radiation

Alpha, Beta & Gamma Radiation (SQA National 5 Physics): Revision Note

Exam code: X857 75

Leander Oates

Written by: Leander Oates

Reviewed by: Katie M

Updated on

Alpha, beta & gamma radiation

  • Radioactive decay is a change in an unstable nucleus that can result in the emission of one of the following types of radiation:

    • Alpha (α) particles

    • Beta (β-) particles

    • Gamma (γ) radiation

Diagram comparing alpha particles (2 protons, 2 neutrons), beta particles (electrons), and gamma rays (EM waves) with illustrations.
Alpha particles, beta particles and gamma waves can be emitted from unstable nuclei

  • Radioactive decay is spontaneous and random

Alpha particles

  • The radiation symbol for alpha is α

  • An alpha particle is the same as a helium nucleus

    • This is because they consist of two neutrons and two protons

  • Alpha particles have a charge of +2

    • This is because they consist of two protons that each have a positive charge

  • Alpha particles can be affected by an electric field due to their charge

Beta particles

  • The radiation symbol for beta is β-

  • Beta particles are fast-moving, high-energy electrons

  • Beta particles have a charge of -1

    • This is because electrons have a negative charge

  • Beta particles can be affected by an electric field due to their charge

Gamma rays

  • The radiation symbol for gamma is γ

  • Gamma rays are electromagnetic waves

  • They have the highest energy of the different types of electromagnetic waves

  • Gamma rays have no charge

  • Therefore, gamma rays are not affected by an electric field

Alpha, beta & gamma radiation in an electric field

Diagram showing paths of alpha particles deflected by positive charge, beta particles deflected by negative charge, and gamma rays unaffected.
Alpha and beta particles are oppositely deflected in an electric field due to their charges, whereas gamma radiation is unaffected because it has no charge

Worked Example

An unidentified form of nuclear radiation is passed through an electric field and is deflected toward the positive plate.

Identify the form of radiation and explain your reasoning.

Answer:

  • The radiation is deflected in an electric field, therefore it must have a charge

  • The radiation is deflected toward the positive plate, therefore its charge must be negative

  • The only form of nuclear radiation with a negative charge is beta radiation, because beta particles are high-energy electrons

Examiner Tips and Tricks

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    Author
    Reviewer
    Leander Oates

    Author: Leander Oates

    Expertise: Physics Content Creator

    Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.

    Katie M

    Reviewer: Katie M

    Expertise: Physics Content Creator

    Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.