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Refraction Refraction • Light can bend not only when it reaches a reflective surface but also when it goes from one medium to another • Medium (pl. media) – The substance or material that light is traveling through Identify the media through which light is traveling in this example. Describe what happens to the wave of light. Identify the media through which light is traveling in this example. (What is the fisherman’s problem?) “Come here, fishy fishy…” Can you think of other examples of refraction between air and water? Refraction • The change in the direction of light when it crosses a boundary between two media. • The effect is only noticeable when the media have different densities. Densities • Order the list of materials from least to most dense: water, glass, air – Air – Water – Glass • When light travels between these media it will change direction – It will slow down as it goes from less dense to more dense – or speed up as it goes from more dense to less dense What causes refraction? incident ray normal i Because water is more dense than air the refracted ray slows down which bends the angle towards the normal air water refracted ray R angle of refraction (R) Water reflects and refracts light At large angles of incidence most of the light reflects and less refracts Water reflects and refracts light At small angles of incidence most of the light enters the water and refracts This explains why you only see a small area underwater directly under where light penetrates the water. Predict what will happen to the refracted ray in each case: normal Incident ray air i glass Will the refracted ray bend towards or away from the normal? Predict what will happen to the refracted ray in each case: normal Incident ray air i glass R The angle of refraction is smaller (glass is more dense so light slows down) and the refracted ray will be bent towards the normal. Predict what will happen to the refracted ray in each case: normal Incident ray water i air Will the refracted ray bend towards or away from the normal? Predict what will happen to the refracted ray in each case: normal Incident ray water air i R Refracted ray The angle of refraction is greater (air is less dense so light speeds up) and the refracted ray will be bent away from the normal.
