Waves

• Waves

  Transfer energy
• Transverse waves

  • Particles oscillate (vibrate) at right angles to the direction of the wave
  • Examples: light, water waves
• Longitudinal waves

  • Particles oscillate in the same direction as the motion of the wave
• Sound is a longitudinal wave
• Wavelength

  The distance between consecutive peaks or troughs in a wave
• Properties of waves


  • Wavelength
  • Amplitude
  • Frequency
  • Period
• Wavelength


  Distance between any two identical points on a wave
• Peak


  Highest point of a wave
• Amplitude


  Half the vertical distance between peak and trough
• Period


  Time it takes for one wave to pass a point
• Frequency


  Number of waves that pass a point in one second
• Equations


  1. Speed = Frequency x Wavelength

  2. Frequency = 1 / Period
• Diffraction


  The spreading out of waves around obstacles or through gaps
• Long wavelengths diffract more than short wavelengths
• Practical uses of diffraction


  • TV waves
  • Radio waves
• At the house, TV waves would be blocked by the mountain

  Due to their large wavelength, they diffract around the mountain
• At the house, radio waves would have good reception


  Because they would not be blocked by the mountain
• Amplitude


  The size or magnitude of a wave
• Ultrasounds have a high frequency and large amplitude
• Humans can hear sounds between 20Hz and 20,000Hz
• The electromagnetic spectrum


  • Radio
  • Microwaves
  • Infrared
  • Visible
  • Ultraviolet
  • X-rays
  • Gamma rays
• The electromagnetic waves all travel at the speed of light (3x10^8 m/s)
• Refraction


  The change in speed and wavelength of a wave as it moves from one medium to another
• When light passes from air to glass, the speed decreases, the wavelength decreases, but the frequency stays the same