Waves

Waves

1. Reflection and Refraction

   • Refraction
     • Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass
       • This causes them to change direction and this effect is called refraction
     • Refraction doesn't happen if the waves cross the boundary at an angle of 90° - in that case they carry straight on
   • Reflection
     • The light is reflected because of the change in density
       • Whenever a wave reaches a medium with a different density some of the wave is reflected at the boundary
     • When a wave hits a boundary between one medium and another some of its energy is reflected
     • The angle of reflection (r) is equal to the angle of incidence (I)

2. Wave Speed

   • Speed = frequency x Wavelength
     • v = f x λ
   • Wave Speed = distance/time

3. What they are

   • Waves are vibrations that transfer energy from place to place without matter being transferred
   • The substance which a wave travels through is known as the medium, and it can be solid, liquid or gas
     • Examples include sound waves and seismic waves
     • It is the medium that vibrates as the waves travel through

4. Transverse and Longitudinal Waves

   • Transverse waves
     • Examples include EM radiation, Light, water and S waves
     • The vibrations are at 90 degrees to the direction of travel of the wave
   • Longitudinal waves
     • Examples include sound, Ultrasound and P waves
     • The vibrations are along the same direction as the wave is travelling

5. Amplitude, Wavelength and Frequency

   • Wavelength is the distance from one peak to the next
   • Frequency is how many complete waves there are per second
     • It is measured in Hertz (Hz)
   • The amplitude is the height of the peak from the mid-line to the peak
   • Speed is how fast it goes

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