25.3: The Law of Refraction - Physics LibreTexts
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WebFeb 20, 2022 · We define the index of refraction n of a material to be. n = c v, where v is the observed speed of light in the material. Since the speed of light is always less than c in matter and equals c only in a vacuum, the index of refraction is always greater than or equal to one. That is, n > 1.
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