Waves

• Waves are one of the ways in which energy may be transferred
• waves transfers energy but don't transfer matter
• Peak


  Highest point
• Trough


  Lowest point
• Amplitude


  The maximum displacement of a point on a wave from its undisturbed position
• Wavelength


  The distance from a point on one wave to the corresponding point on the adjacent wave
• Frequency


  The number of waves passing a point each second
• Wave speed


  The speed at which the energy is transferred through the medium
• Wave speed = frequency x wavelength
• Electromagnetic waves


  • Transverse waves
  • Can transfer energy
  • Can travel through a vacuum (space)
  • Travel at the same speed through a vacuum or air at 300 million m/s
• Electromagnetic spectrum


  • Visible light
  • Ultraviolet
  • Microwave
  • X-rays and gamma rays
  • Radio waves
  • Infrared
• Visible light


  Contains all the frequencies that can be detected by the human eye
• Red light has the lowest frequency, visible light has the highest frequency
• Longitudinal waves


  • Vibrations are in the same direction as the wave
  • Examples: sound, ultrasound, seismic waves
  • Show regions of compression and rarefaction
• Transverse waves


  • Vibrations are at right angles to the direction of the wave
  • Examples: ripples on water, electromagnetic waves, S-waves
• Ultraviolet


  • Cannot be seen
  • Has hazardous effects on the body, can cause skin to tan and age prematurely
  • Can be used to make efficient lamps
• Microwaves


  • Used for cooking food and satellite communications
  • Easily absorbed by food, causing heating by increasing the internal energy of molecules
• 1. rays and gamma rays

  • Produced by changes in the form of nuclear radiation
  • Transmitted through body tissues with little absorption
  • Ideal for internal imaging, but can also cause mutation of genes and lead to cancer
• Radio waves


  • Used for communication (e.g. TV, radio)
  • Transmitted easily through air and do not damage the human body
  • Can be reflected to change direction, ideal for communication
  • Can be produced by oscillations in electrical circuits
• Infrared


  • Used by electrical heaters, for cooking food, and in infrared cameras
  • Absorbed by chemical bonds, increasing their internal energy and causing heating
• Visible light


  • The light we can see
  • Used in fibre optic communications, where coded pulses of light travel through glass fibres
• Longitudinal waves


  Wave that moves in the same direction as the vibrations
• Transverse waves


  Vibrations are at right angles to the direction of the wave
• Longitudinal waves


  • Sound waves
  • Ultrasound waves
• In longitudinal waves, particles are vibrating
• Transverse waves


  • Ripples on the surface of water
  • Seismic waves
  • Electromagnetic waves
• Longitudinal waves


  • Show bands of compression and rarefaction
  • Compressions are regions of high pressure due to particles being close together
  • Rarefactions are regions of low pressure due to particles being spread further apart