Index of refraction (23-5)

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Question

Speed of light in the medium

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Review

The index of refraction of vacuum is 1, since light travels at the speed of light $c$ so $v = c$ and $n = c/c = 1$ . In any material medium, light travels slower than $c$ , so $v < c$ and $n > 1$ . The greater the value of the index of refraction $n$ in a given medium, the slower the speed $v$ at which light propagates in that medium. Table 23-1 lists the index of refraction of some common materials. Note that the index of refraction of air is equal to one to three significant digits, so we’ll often take $n_{\mathrm{air}} = 1$ in calculations.