Properties of EM Waves (OCR GCSE Physics A (Gateway)): Revision Note

Properties of EM Waves

• 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

Transfer of Energy by EM Waves

• 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 enable humans to produce vitamin D, which is needed for healthy bones, teeth and muscles