Types of Radiation (WJEC GCSE Physics)

• When an unstable nucleus decays, it emits radiation
• The different types of radiation that can be emitted are:
  • Alpha (α) particles
  • Beta (β^-) particles
  • Gamma (γ) radiation

• These changes are spontaneous and random

Alpha Particles

• The symbol for alpha is α
• An alpha particle is the same as a helium nucleus
• This is because it consists of two neutrons and two protons

Beta Particles

• The symbol for beta is β⁻
• Beta particles are high-energy electrons
• They are produced in nuclei when a neutron changes into a proton and an electron

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

Alpha, Beta & Gamma Radiation

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

Properties of Alpha, Beta & Gamma

• Alpha (α), beta (β) and gamma (γ) radiation can be identified by their:
  • Nature (what type of particle or radiation they are)
  • Ionising ability (how easily they ionise other atoms)
  • Penetrating power (how far can they travel before they are stopped completely)

• Alpha, beta and gamma penetrate materials in different ways
• This means they are stopped, or reduced, by different materials

Penetrating Power of Alpha, Beta and Gamma

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 rays can pass through aluminium but are only partially stopped by thick lead

Summary of the properties of nuclear radiation

Particle	Nature	Range in air	Penetrating power	Ionising ability
Alpha (α)	helium nucleus (2 protons, 2 neutrons)	a few cm	low; stopped by a thin sheet of paper	high
Beta (β)	high-energy electron	a few 10s of cm	moderate; stopped by a few mm of aluminium foil or Perspex	moderate
Gamma (γ)	electromagnetic wave	infinite	high; reduced by a few cm of lead	low

 

Dangers of Nuclear Radiation

• All types of ionising radiation pose a danger if mishandled as they can damage living cells and tissues and can even cause cancer

Effect of Radiation on a Human Cell

Ionising radiation can cause damage to DNA. Sometimes the cell can successfully repair the DNA, but incorrect repairs can cause a mutation

• Highly ionising types of radiation are more dangerous inside the body (if a radioactive source is somehow ingested)
  • Alpha sources are the most ionising, so they are likely to cause the most harm to living cells inside the body
  • Gamma sources are the least ionising (about 20 times lower than alpha particles), so they are likely to cause the least harm to living cells inside the body

• Highly penetrating types of radiation are more dangerous outside the body
  • Gamma sources are the most penetrating, so they are able to pass through the skin and reach living cells in the body
  • Alpha sources are least penetrating, so they would be absorbed by the air before even reaching the skin

Nuclear Waste

• Nuclear waste must be treated appropriately, depending on the type of radiation it emits
  • Alpha-emitting nuclear waste is easily stored in plastic or metal canisters
  • Beta-emitting nuclear waste is stored inside metal canisters and concrete silos
  • Gamma-emitting nuclear waste requires storage inside lead-lined, thick concrete silos
• Radioactive waste of all types tends to emit dangerous levels of radiation for many years, so it must be stored securely for a very long time
• Typically, waste with the highest levels of radioactivity must be buried underground in secure, geologically stable locations

Dealing with Radioactive Waste

Depending on the type of radiation emitted, nuclear waste is treated in different ways