Electromagnetic Waves

• Electromagnetic waves are transverse waves.
• Electromagnetic waves are not mechanical waves because they can travel through a vacuum.
• EM waves transfer energy from their source to their absorber.
• Longest wavelength/lowest frequency

  Radio waves

  Microwaves

  Infrared

  Visible light (red - green - blue)

  Ultraviolet light

  X-rays

  Gamma rays

  Shortest wavelength/highest frequency
• EM waves can be produced by changes inside an atom / atomic nucleus.
• Gamma rays are produced by changes in the nucleus of an atom such as through radioactive decay.
• Radio waves can be produced through oscillations in an electrical circuit.
• Radio waves can be detected by being absorbed and creating an alternating current in a circuit with the same frequency as the radio wave.
• Radio wave transmit:

  • Television signals
  • Mobile phone signals
  • Bluetooth signals.
• Microwave uses:

  • Satellite communications
  • Cooking food
• Infrared radiation uses:

  • Heating
  • Remote controls
  • Infrared cameras
  • Cooking food
• Harmful EM waves:

  • Ultraviolet light
  • X-rays
  • Gamma rays
• Ultraviolet light hazards:

  • Damage skin cells
  • Sunburn
  • Increase risk of skin cancer
  • Age skin prematurely
  • Blindness
• X-rays are used for medical imaging because they pass through flesh but not bone.
• Gamma rays are used for treating cancer and sterilising medical equipment because high doses kill cells and bacteria.
• Refraction is when waves change speed and direction as they cross the boundary from one substance to another due to the change in velocity.
• A refracted EM wave bends towards the normal when it slows down as it crosses the boundary from one substance to another.