Properties of EM Waves (OCR Gateway GCSE Physics: Combined Science)

• Electromagnetic waves are defined as:

Transverse waves that transfer energy from the source of the waves to an absorber

• All electromagnetic waves share the following properties:
  • They are all transverse
  • They can all travel through a vacuum
  • They all travel at the same speed in a vacuum

• There are 7 types of electromagnetic waves, which all together form a continuous spectrum called the Electromagnetic spectrum

• Electromagnetic (EM) waves carry energy and so can transfer energy from one point to another point
  • This is from a source to an absorber
  • E.g. From the sun to our skin
• EM waves with a shorter wavelength carry a higher energy
  • This includes UV, X-rays and gamma rays

• The higher the energy of the EM wave, the more dangerous it is

Energy Transfer by Microwaves

• Water molecules absorb certain wavelengths of microwave radiation
• Therefore, microwave ovens transfer energy from the electronics to heat the food placed inside it

Energy transfer in a microwave oven

Energy Transfer by Infrared

• All hot objects emit infrared radiation
• The emitted waves can then be absorbed by other objects, warming them up

Energy Transfers from the Sun

• The Sun emits several types of EM radiation, including:
  • Visible light waves allow living creatures to see
  • Infrared waves heat up the Earth
  • Ultraviolet waves provide plants with the energy for photosynthesis which they need to grow