AQA GCSE Physics

Revision Notes

4.2.2 Types of Radiation

Types of Radiation

  • When an unstable nucleus decays it emits radiation, called nuclear radiation
  • There are different types of radiation that can be emitted:
    • Alpha
    • Beta
    • Gamma
    • Neutrons

Alpha Particles

  • The 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 means they can be affected by an electric field

Beta Particles

  • The symbol for beta is β
  • Beta particles are fast-moving electrons
  • They are produced in nuclei when a neutron changes into a proton and an electron
  • Beta particles have a charge of -1
    • This means they can be affected by an electric field

Gamma Rays

  • The 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

Neutrons

  • The symbol for a neutron is n
  • Neutrons are one of the two particles found in the nucleus of atoms
  • Neutrons are neutral, they have no charge

Types of radiation new, downloadable IGCSE & GCSE Physics revision notes

Alpha particles, beta particles, gamma waves and neutrons can be emitted from unstable nuclei

Properties of Alpha, Beta and Gamma Radiation

  • The properties of Alpha, Beta and Gamma are given in this table, and then described in more detail below

Different Properties of Nuclear Radiation

Comparison table, downloadable IGCSE & GCSE Physics revision notes

  • The trend down the table shows:
    • The range increases
    • Penetrating power increases
    • Ionisation decreases

Penetrating Power

  • Alpha, beta and gamma have different properties
  • They penetrate materials in different ways
    • This means they are stopped by different materials

penetration increase, IGCSE & GCSE Physics revision notes

Alpha, beta and gamma are different in how they penetrate materials. Alpha is the least penetrating, and gamma is the most penetrating

  • Alpha is stopped by paper, whereas beta and gamma pass through it
  • Beta is stopped by a few millimetres of aluminium
    • Gamma can pass through aluminium
  • Gamma rays are only partially stopped by thick lead

Ionising Power

  • All nuclear radiation is capable of ionising atoms that it hits
  • When an atom is ionised, the number of electrons it has changes
  • This gives it a non-zero charge

ionising-the-atom, IGCSE & GCSE Physics revision notes

When radiation passes close to atoms it can knock out electrons, ionising the atom

  • Alpha radiation is the most ionising form of nuclear radiation
    • This is because alpha particles have a charge of +2
  • Gamma radiation is the least ionising form of nuclear radiation

Range in Air

  • The more ionising a form of radiation is, the sooner it will react with the air it is moving through
  • Strongly ionising radiation has the shortest range in air
    • Alpha only travels a few centimetres in air
    • Beta has a range of a few tens of centimetres
    • Gamma is not absorbed by air and so has an infinite range, although it does get less intense with distance

Worked Example

A student has an unknown radioactive source. They are trying to work which type of radiation is being given off:

A    Alpha particles
B    Beta particles
C    Gamma rays
D    Neutrons

They measure the count-rate, using a Geiger-Muller tube, when the source is placed behind different material. Their results are shown in the table below:

WE Absorption table, downloadable IGCSE & GCSE Physics revision notes

Which type of radiation is being given off by the source?

ANSWER:  B

    • The answer is not A because the radiation passed through the paper almost unchanged
      • This means it is not alpha
    • The answer is not C or D because the aluminium decreased the count-rate significantly
      • This means it is not gamma (gamma penetrates aluminium)
      • This also means it is not neutrons (neutrons penetrate aluminium, however you do not need to know this for your GCSE)
    • Therefore, the source must be Beta particles

Exam Tip

Make sure to memorise the different types of radiation, as these are common exam questions. However, neutron radiation is less common and it is not required to know its properties for the exam

Author: Katie

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.
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