Waves

• Wave


  Transfers energy without matter being banged
• Wave


  • Peak
  • Crest
  • Trough
• Wavelength


  The distance between the peak and the trough
• Amplitude


  Maximum displacement from equilibrium
• Frequency


  The number of waves passing a certain point every second
• Period


  Time for one complete wave to pass a certain point
• Transverse wave


  • Oscillations are at right angles to the direction of energy transfer
• Longitudinal wave


  • Oscillations are parallel to the direction of energy transfer
• Electromagnetic spectrum


  • Radio
  • Microwave
  • Infrared
  • Visible
  • Ultraviolet
  • X-ray
  • Gamma ray
• Electromagnetic waves travel at 300 million m/s in a vacuum
• Electromagnetic waves can be reflected, refracted, and diffracted
• Electromagnetic waves can travel through a vacuum
• Electromagnetic waves have a range of wavelengths and frequencies
• Electromagnetic waves with shorter wavelengths have higher frequencies and higher energies
• Doppler effect


  Change in observed frequency of a wave due to relative motion between the source and the observer
• When a sound source moves towards an observer

  The wave bunch together, resulting in a higher pitch, shorter wavelength, and higher frequency
• When a sound source moves away from an observer


  The waves spread out, resulting in a lower pitch, longer wavelength, and lower frequency
• Reflection


  • Angle of incidence equals angle of reflection
  • Normal is at 90 degrees to the surface where the ray hits
• Refraction


  • When light travels from a less dense to a more dense medium, it bends towards the normal
  • Critical angle is the angle of incidence when the angle of refraction is 90 degrees
• Total internal reflection


  • Occurs when light travels from a more dense to a less dense medium and the angle of incidence is greater than the critical angle
  • Allows light to be guided through optical fibres
• Using a prism to measure refractive index


  1. Shine light into prism

  2. Mark emergent ray

  3. Join incident and emergent rays

  4. Measure angles of incidence and refraction

  5. Calculate sin(i)/sin(r) to find refractive index
• Optical fibres


  • Core has higher refractive index than cladding
  • Advantages: transfer more data, less susceptible to interference, can travel further before being amplified