Waves and wave properties

Reflection and refraction

For reflection, where θ is the angle to the normal of the surface, θi = θr; i = angle of incidence, r = angle of reflection.

Refraction

The slowing down of light (e.g. when it enters another medium).

The core equations to remember are: n = ci ÷ c r = (sinθi) ÷ (sinθr) = nr ÷ ni. c is the speed of light, n is the refractive index of the material. See Snell's law.

Total internal reflection will only happen when θi > θc, where θc is the critical angle. If θi = θc, then the light will be refracted on the 'edge', parallel to the material. If θi < θc, waves will be refracted. The angle θc can be calculated by n = sin-1θc.

A diagram of basic refraction

v = ƒ × λ, where v is the velocity of the wave in ms-1, ƒ is the frequency of the wave in Hertz and λ is the wavelength. Period is the time taken for the wave to go back to its original state in seconds. So, T = 1 ÷ ƒ