Waves

• Transverse waves have oscillations perpendicular to the direction of energy transfer.
• Longitudinal waves have oscillations parallel to the direction of energy transfer.
• Amplitude is the height of a wave from 0
• Transverse

  • can travel through a vacuum
  • contains peaks & troughs
  • eg. x-rays, microwaves, visible light, radio waves
• Longitudinal

  • can't travel through a vacuum
  • must travel through a medium
  • contains compressions & rarefactions
  • eg. sound waves
• Period is the time taken for 1 complete oscillation
• Wavelength is the distance between 2 identical points.
• Frequency is number of waves per second.
• Ripple Tank Practical

  • Find frequency by counting no. of waves passing a point in 10s. Divide this by 10 for the frequency.
• Ripple Tank Practical

  • Find wavelength - count no. of waves in 30cm [using a ruler]. Divide 30cm [convert to meters first] by no. of waves
• Humans can hear frequencies between 20 and 20,000 Hz.
• Sound travels fastest through liquid mediums.
• High pitch = high frequency

  High sound = high amplitude
• Black is the best absorber of infrared radiation
• Speed of sound in air is 330 m/s
• Ultrasound advantages

  • non invasive
  • non ionising
  • helps identify different tissues
  • can build up clear images
• Ultrasounds are commonly used for

  • pregnancy
  • diagnosis
  • breakdown of tissues
• Electromagnetic spectrum from left to right

  • radio waves
  • micro waves
  • infrared
  • visible light
  • ultraviolet
  • x-ray
  • gamma
• Convex lenses converge light
• Concave lenses diverge light
• The primary colours are Red, Green and Blue
• The secondary colours are magenta, yellow and cyan
• Filters only allow their colour through and absorbs any others.
• Wave is the transfer of energy without matter