The Electromagnetic Spectrum

• The Electromagnetic Spectrum (EM)

  • A continuous range of different wavelengths
  • Transverse
  • All travel at the same speed (about 300 million m/s)
  • Can travel in a vacuum
• The sevem distinct types of EM waves

  • Radio Waves
  • Microwaves
  • Infrared (IR) Radiation
  • Visible Light
  • Ultravaiolet (UV) Radiation
  • X-Rays
  • Gamma Rays
• Radio Waves

  • Used in communications
  • E.g. traditional radio and TV
  • Longwave radio transmits info around the Earth
  • Wavelength of 1-10km
  • Shortwave radio can be bounced off the atmosphere
  • Wavelength of 10-100m
  • Signals are then picked up by transmitters
• Microwaves

  • Also used in communications
  • Wavelength of 1-10cm
  • Often used by satellites
  • Microwaves are used in mobile phones and Wi-Fi
  • Microwaves are also used to heat food
  • Heat up the water molecules inside the food, causing it to cook
• Infrared (IR) Radiation

  • Heat radiation
  • Used in convention cooking and electric heaters
  • All objects release IR radiation (hot release more than cold)
  • Can be detected using specialised equipment
  • E.g. night vision goggles
• Visible Light

  • Used in optical fibres
  • Fibreoptics, used to carry data
  • Bouced off the inside of an optical core
  • Used in broadband and telephone lines
  • Used for photography
  • Amount of light that hits the sensor is controlled by both aperture and shutter speed
• Ultraviolet (UV) Radiation

  • Often used in combination with Flourescent bulbs
  • Absorb UV radiation and release visible light
  • Energy efficient
  • UV is also found in sunlight
  • People sunbathe to achieve a suntan
• X-Rays

  • Used in medical imaging
  • To look at internal structures of the human body
  • They can penetrate (go inside) the body
  • Detected using a detector plate
  • Denser regions of the body absorb more x-rays
  • Show up more brightly on a photograph
  • Used to diagnose broken bones
  • More dense so they show up as bright white on a photograph
• Gamma Rays (γ)

  • Harmful to all forms of life
  • Cause cancer and cell mutation
  • Used to sterilise medical equipment
  • Useful to kill pathogens and other microorganisms
  • Also used to sterilised food
  • Can also be used to preserve food for longer
• Radiation types, their uses and their dangers

  • Gamma Rays:
  • Uses: Treating cancer, sterilisation
  • Dangers: Cancer, cell mutation
  • X-Rays:
  • Uses: Medical
  • Dangers: Cancer, cell mutation
  • UV:
  • Uses: Sun tanning
  • Dangers: Damage to cells & blinding
  • Visible light:
  • Uses: Seeing things, fibre optic cables
  • Dangers: None (unless looking at the sun)
  • IR:
  • Uses: Remote controls, heat transfer
  • Dangers: Skin burns
  • Microwaves:
  • Uses: Satellites, phones
  • Dangers: Internal healting of body tissue
  • Radiowaves:
  • Uses: Communications
  • Dangers: Very few