Types of Radiation (AQA GCSE Physics)

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

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

• 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

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

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