I know that refraction occurs when a light enters a medium that was optically denser/optically rarer than the medium it was travelling through. Why does the light ray have to refract or bend at all? (What difference does it make if the medium is denser or rarer?)

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anonymous · Answer

p.s. i know that the speed of light is different in each medium, but  i dont see how that affects anything.

anonymous · Answer

http://en.wikipedia.org/wiki/Refraction Refraction occurs when waves travel from a medium with a given refractive index to a medium with another at an angle. At the boundary between the media, the wave's phase velocity is altered, usually causing a change in direction. Its wavelength increases or decreases but its frequency remains constant. For example, a light ray will refract as it enters and leaves glass, assuming there is a change in refractive index.