Refraction

Refraction

1. Refraction - Waves Change Speed and Direction NOT FREQUENCY

   • The speed of a wave is affected by the density of the substance or medium it is travelling in, light waves travel more slowly in a denser medium
   • if the speed of the wave changes so does the wavelength because of wave speed = frequency x wavelength, if speed decreases the wavelength must also decrease. The change in speed and wavelength can cause the wave to change direction this is called refraction
   • If a light wave hits a boundary face on it slows down but carries on in the same direction. If it doesnt hit it flat on the wave hits the boundary first and slows down while another part carries on at the first, faster speed for a while this mean it has been refracted
   • Converging or convex lenses use refraction to focus light waves to form an image of an object. As a light ray hits the surface of a lens and passes from air to glass it slows down. This causes the light ray to bend towards the normal. When it hits the glass to air boundary it speeds up and bends away from the normal. The curvature of the lens means all the parallel rays hitting different parts of the lens are bent rowards the same focal point where an image is formed.

2. A triangular Prism can refract light to form a spectrum

   • Different wavelenghts refract by different amounts. So white light sisperses into its different colours as it enters a prism. A rectangular prism has parallel boundaries so the rays bend one way as they enter and then bend back by the same amount as they lave. With a triangular prism the boundaries arent parallel which means the different wavelenghts dont recomnbine and you get a spectrum