Physics - Waves

Physics - Waves

1. There are two types of waves

   • Transverse waves
     • Most waves are transverse: light, x-rays, mexican
     • Trans means across: particles vibrate up and down and wave moves oscillate
   • Longitudinal waves
     • There are only a few types of these waves: seismic, sound
     • Particles vibrate left and right, wave moves across

2. Speed

   • Speed of sound in air: 300m/s
   • Speed of light in air: 300,000,000m/s

3. Reflection

   • The angle of incidence = the angle of reflection

4. The Electromagnetic spectrum

   • The Electromagnetic spectrum covers many wavelengths and wave energies.
   • Lowest energy = radio waves
   • Highest = gamma rays
   • Electromagnetic waves are vibrations of magnetic and electric fields

5. Refraction

   • Refraction is the change in direction of a wave due to a change in its transmission medium.
     • Different colours of light have different frequencies. This means that they are refracted by different amounts
     • This is noticeable when the light is refracted twice in the same direction e.g. through prisms/ raindrops
     • Wavelength has reduced and the frequency has stayed the same
       • Veloctiy has decreased
   • TIR (Total Internal Refraction)
     • If the light comes out of a dense material at a shallow angle, the light will be reflected and won't come out at all
       • i < critical angle
       • i = critical angle (42 degrees)
       • i > critical angle

6. Diffraction

   • Diffraction is the spreading out of waves
   • if a wave passes through a gap the same size or smaller than it wavelength, it diffracts

7. Gatso speed cameras

   • The camera sends out a radio wave. The wave is reflected off the rear off the car. Because the car is moving, the frequency of the received wave will be changed.

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