Wed January 02, 2013 By:

sir please explain me about the snell's law in brief and also about relative and the absolute refractive index

Expert Reply
Wed January 02, 2013
Relative refractive index is refractive index of a medium with respect to another medium

Absolute refractive index is refractive index of a medium with respect to vacuum.
Refractive index, also called index of refraction, measure of the bending of a ray of light when passing from one medium into another. If i is the angle of incidence of a ray in vacuum (angle between the incoming ray and the perpendicular to the surface of a medium, called the normal), and r is the angle of refraction (angle between the ray in the medium and the normal), the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction; i.e., n = sin i / sin r. Refractive index is also equal to the velocity c of light of a given wavelength in empty space divided by its velocity v in a substance, or n = c/v. Some typical refractive indices for yellow light (wavelength equal to 589 nanometres [10-9 metre]) are the following: air, 1.0002; water, 1.333; crown glass, 1.517; dense flint glass, 1.655; and diamond, 2.417. The variation of refractive index with wavelength is the source of chromatic aberration in lenses .
The refractive index of a medium is directly proportional to the optical density of the medium. For ag. the r.i. of flint glass is 1.66 and that of water is 1.33. Since glass has a higher refractive index than water , therefore glass is optically denser than water and more bending of light takes place in glass than in water. 
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