| Themes > Science > Physics > Optics > Optical Instruments , Principles & Applications > Mirror > The Index of Refraction and the Speed of Light |
Recall that refraction occurs because the light changes speed as it enters a new medium. The light slows down if it enters a more optically dense medium and speeds up as it enters a less optically dense medium. The least optically dense medium of all is a vacuum—in this medium light travels at its fastest speed. In all other media it travels slower. It can be shown that the index of refraction is a ratio of the speeds of light in the respective media. In fact, the index of refraction is defined to be the comparison of the speed in a vacuum to the speed of light in a substance: ex.
The index of refraction for water is 1.33. Find the speed of light
in water. Try-It-Yourself: 1. The speed of light in
a certain plastic is 2.31 x 108 m/s. Calculate the index of
refraction of the plastic. 2. The index of
refraction of diamond is 2.42. Calculate the speed of light in diamond. Answers: 1. ns = 1.30 2. vs = 1.24 x 108 m/s |
|
|