UNIT 1 PHYSICS

• Transverse wave

  Oscillations are perpendicular to the direction of energy transfer
• Longitudinal wave


  Oscillations are parallel to the direction of energy transfer
• Amplitude


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


  Distance from a point on one wave to the equivalent 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
• Reflection


  When a wave bounces off a surface
• Refraction


  When a wave passes into a new medium, causing it to change speed and direction

  
• Sound waves are an example of longitudinal waves – they show compression (particles are pushed together) and rarefaction (particles spread out)

  
• The ripples on a water surface are transverse waves, and so are all electromagnetic waves
• Types of electromagnetic waves

  • Radio waves
  • Microwaves
  • Infrared waves
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays

  
• Radio waves (used for TV, radio and radio telescopes)
• When radio waves are absorbed, they may create an alternating current with the same frequency as the radio wave itself. Likewise, an alternating current can create radio waves with the same frequency that the current alternates.
• Microwaves (used for satellite communications and cooking food)
• Infrared waves (used for electrical heater, cooking food, infrared cameras)
• Visible light (used for fibre optic communications)
• Ultraviolet (used for fluorescent lamps and sun beds)
• 1. rays (used for medical imaging and treatments)
• Gamma rays (used for sterilising surgical instruments and treatment of cancer)
• Light (transverse) is faster than sound (longitudinal) and has a higher frequency
• Shiny surfaces act as mirrors when they reflect waves; rough surfaces scatter waves in all directions.
• Electromagnetic waves change speed when they travel between different substances (e.g. air to glass) which causes them to change direction – this is called refraction
• When waves move into a more dense medium, they are refracted towards the normal line as they slow down (and away from the normal when moving into a less dense medium, as they slow down)
• Wave speed equation


  1. wave speed(m/s) = frequency(Hz) × wavelength(m)

  2. v = f λ

  
• You can also calculate frequency from a diagram, by working out how many waves there would be in 1s (count how many waves are in the time given in the diagram, and the scale up/down to waves per second)

  
• From radio waves to gamma rays: Frequency and energy increase; wavelength decreases; speed is the same in a vacuum