Radiation (WJEC GCSE Physics)

• The term 'radiation' is used to describe:
  • Electromagnetic waves
  • Energy given out by radioactive materials
    • You can find out more about this in our revision note on Types of Radiation

Ionising Radiation

• Radiation from radioactive emissions and short wavelength regions of the electromagnetic spectrum are able to ionise atoms
  • This is referred to as ionising radiation 
• As the frequency of electromagnetic (em) waves increases, so does the energy
• Beyond the visible part of the spectrum, the energy becomes large enough to ionise atoms
• As a result of this, the danger associated with em waves increases along with the frequency
  • The shorter the wavelength, the more ionising the radiation
  • Although the intensity of a wave also plays a very important role

• In general, electromagnetic waves become more dangerous the shorter their wavelength
  • For example, radio waves have no known harmful effects whilst gamma rays can cause cancer and are regarded as extremely dangerous

• Because of ionisation, ultraviolet waves, X-rays and gamma rays can have hazardous effects on human body tissue
  • The effects depend on the type of radiation and the size of the dose
• Ionising radiation can interact with atoms, damaging cells by the energy they carry and causing mutations, making them cancerous

Ionising Regions in the Electromagnetic Spectrum

Ultraviolet, X-rays and gamma rays can all ionise atoms

Uses & Dangers of Electromagnetic Waves

• The properties of electromagnetic waves are determined by their frequency, wavelength and energy so each region of the spectrum has different uses and associated risks

Uses & Dangers of Electromagnetic Waves Table

Wave	Uses	Danger
Radio	Communications (radio and TV)	No known danger
Microwave	Heating food Communication (WiFi, mobile phone,  satellites)	Possible heat damage to internal organs
Infra-red	Heating Remote controls Fibre optic communication	Skin burns
Visible light	Seeing and taking photographs/videos Fibre optic communication	Bright light can cause eye damage
Ultraviolet	Fraud detection Fluorescent bulbs	Ionising Eye damage Sunburn Skin cancer
X-rays	X-Ray images (medicine, airport security and industry)	Ionising Kills cells Causes cell mutations Cancer
Gamma Rays	Sterilising medical instruments Treating cancer	Ionising Kills cells Causes cell mutations Cancer

Microwaves

• Certain frequencies of microwaves are absorbed by water molecules
• Since humans contain a lot of water, there is a risk of internal heating from microwaves
• This might worry some people, but microwaves used in everyday circumstances are proven to be safe
  • Microwaves used for communications (including mobile phones) emit very small amounts of energy which are not known to cause any harm
  • Microwave ovens, on the other hand, emit very large amounts of energy, however, that energy is prevented from escaping the oven by the metal walls and metal grid in the glass door

Ultraviolet

• Ultraviolet is similar to visible light, except it is invisible to the human eye and carries a much higher energy
• If eyes are exposed to high levels of UV it can cause severe eye damage
  • Good quality sunglasses will absorb ultraviolet, preventing it from entering the eyes

• Ultraviolet is ionising meaning it can kill cells or cause them to malfunction, resulting in premature ageing, and diseases such as skin cancer
  • Sunscreen absorbs ultraviolet light, preventing it from damaging the skin

X-rays & Gamma Rays

• X-rays and gamma rays are the most ionising types of EM waves
  • They are able to penetrate the body and cause internal damage
  • They can cause the mutation of genes and cause cancer

• In medical applications, X-ray levels are kept minimal to reduce risk
• Workers handling gamma rays take precautions to minimise exposure