Waves

• Wave


  The propagation of energy / information through a medium or vacuum without any transfer of matter
• Travelling waves


  • Transfer energy
• Standing waves


  • Store energy
• Longitudinal waves


  Waves in which the oscillations of the particles are parallel to the direction of the wave's travel
• Transverse waves


  Waves in which the oscillations of the particles are perpendicular to the direction of the wave's travel
• Amplitude


  The maximum extent of an oscillation, measured from the equilibrium
• Equilibrium


  The horizontal line that is the midpoint of a wave
• Wave-front


  The point where the wave restarts a "cycle" / all the points on a wave which are in the same phase
• Frequency


  The number of wave-fronts passing a point per second, measured in Hertz (Hz)
• Wavelength


  The distance between two wave-fronts, measured in metres (m)
• Wave period


  The amount of time it takes for two successive wave-fronts to pass a fixed point, measured in seconds (s)
• Wave speed


  The speed at which a wave travels, measured in (m/s)
• Wave equations


  1. v = f × λ

  2. f = v ÷ λ

  3. λ = v ÷ f

  4. T = 1/f

  5. f = 1/T
• Electromagnetic (EM) spectrum


  A continuous spectrum of transverse waves which are types of light, with a speed of 3 × 10⁸ m/s in a vacuum
• Amplitude of EM waves


  Proportionate to the brightness/intensity of the light
• Frequency of EM waves

  Denotes where they sit on the spectrum
• Uses of the EM spectrum

  • Radiowaves for broadcasting and communications
  • Microwaves for cooking, satellite transmissions and Wi-Fi
  • Infrared for heaters and night vision
  • Visible light for optical fibres and photography
  • Ultraviolet for fluorescent lamps and seeing bodily fluids
  • X-rays for observing internal structures
  • Gamma rays for sterilising
• Dangers of the EM spectrum

  • Microwaves can heat internal body tissue - prevented by shielding
  • Infrared can cause burns - prevented by heat resistant clothing
  • Visible light can cause retinal damage - don't look directly at intense emitters
  • Ultraviolet can cause skin burns or cataracts - wear normal clothing, sunscreen and sunglasses
  • X-rays and gamma rays increase cancer risk - use lead shielding or stand far away
• Sound waves

  An example of longitudinal waves, with a speed of 343m/s in air
• Amplitude of sound waves

  Directly proportionate to the volume (loudness not capacity) of the sound
• Frequency of sound waves

  Directly proportionate to the pitch