Waves

• Types of waves

  • Longitudinal
  • Transverse
• Transverse wave

  • Vibrations at 90º to the direction of travel
• Longitudinal wave

  • Vibrations parallel to the direction of travel
• Refraction

  1. Change in direction

  2. Change in wavelength due to change in speed
• Reflection

  1. Wavelength does not change

  2. Angle from normal to wave when it hits object is the same as when it is reflected
• Satellite types

  • Geosynchronous
  • Geostationary
• Geosynchronous satellite

  • Returns to the same point once every 24 hours
• Geostationary satellite

  • Stays above the same point at all times
• Using geostationary satellites to send messages

  1. Requires at least 3 satellites

  2. Signal must travel up to satellite and back

  3. Cannot travel straight from one satellite to another without returning to a station on the ground first
• Wave speed


  • Distance (m) / Time (s)
  • Wavelength (m) x Frequency (Hz)
• There are two complete waves shown in the example
• Wave

  • Wavelength = length of one complete wave
  • Amplitude = maximum displacement
  • Frequency = number of waves in 1 second
• Parts of the electromagnetic spectrum

  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X rays
  • Gamma rays
• Electromagnetic spectrum

  • All parts transfer energy
  • All are transverse waves
  • All travel at the same speed in a vacuum (3 x 10^8 m/s)
  • Have different properties and uses
• Properties of electromagnetic spectrum

  • Wavelength (long to short)
  • Frequency (low to high)
  • Energy (low to high)
  • Danger (low to high)
• Uses of electromagnetic spectrum

  • Radio, television, satellite television
  • Mobile phones, cooking food, optical fibres, remote controls, heat treatment
  • Visible light
  • Fraud detection
  • Looking at broken bones
  • Killing cancer cells
  • Penetrating deep water