The ratio of the speed of light in a vacuum to the speed of light in a medium under consideration.
The ratio of the sine of the angle of incidence to the sine of the angle of refraction for a ray of light crossing from one medium into another.
A measure of the extent to which a substance slows down light waves passing through it. The index of refraction of a substance is equal to the ratio of the velocity of light in a vacuum to its speed in that substance. Its value determines the extent to which light is refracted when entering or leaving the substance.
Since the angles of incidence and refraction are connected by the relation sin i=µ sin r (Snell's Law), µ being the index of refraction of the medium, then the problem may be stated as follows: to determine the value of the angle i which makes D = 2 (i - r) +n (7r - 2r) a maximum or minimum, in which i and r are connected by the relation sin i =µ sin r, µ being a constant.
The amount of separation is very small, and depends on the thickness of the glass, the index of refraction and the focal length of the telescope.
The refraction of light passing through sea-water is dependent on the salinity to the extent that the index of refraction is greater as the salinity increases.
Sarasin and longer series of experiments by Tornde and Kriimmel this relation is shown to be so close that the salinity of a sample can be ascertained by determining the index of refraction.
broad according to Zopf), highly refractive and colourless (or very dark, probably owing to the high index of refraction and minute size).