P1.5

P1.5

1. The Nature of waves

   • We use waves to transfer energy and information
   • Transverse waves vibrate at right angles to the direction of travel
   • All electromagnetic waves are transverse
   • Longitudinal waves vibrate parallel to the direction of energy transfer
   • Sound waves are longitudinal
   • Electromagnetic waves
     • Gamma rays
     • X-rays
     • light waves
     • Radio waves

2. Measuring Waves

   • Amplitude = height from rest point
     • Greater amplitude the more energy it carries
   • Wavelength = peak to peak or trough to trough
   • Frequency = number of waves passing through one point in one second
   • Speed of a wave equation: wave speed-v (m/s) = frequency-f (Hz) x wavelength- (m)

3. Sound

   • Frequency range of the human ear = 20Hz to 20kHz
   • Sound waves are longitudinal
   • Sound waves need a medium to travel in
   • Reflections of sounds are called echos
   • High frequency = high pitch
   • high amplitude = loud

4. Wave properties

   • Reflection
     • Normal line is perpendicular to the reflective surface
     • Angle or incidence = Angle of rreflection
     • Real image: one that can be formed on a screen
     • Virtual image: cannot be formed on a screen because the rays that form it would pass through it
   • Refraction
     • Refraction of light is the change of direction of a light ray when it crosses a boundary between two transparent substances
     • If the speed is decreased it is refracted towards the normal
     • If the speed is increased it is refracted away from the normal
   • Diffraction
     • Diffraction is the spreading out of waves when they pass through a gap
     • The narrower the gap the greater the diffraction
     • If radio waves do not diffract enough when they go over hills they will not be transfered well resulting in poor signal or TV connection