plz..xplain d concept of sin or theta related 2 refraction of light..

Snell's law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media, or equivalent to the opposite ratio of the indices of refraction:

with each  as the angle measured from the normal,  as the velocity of light in the respective medium (SI units are meters per second, or m/s) and  as the refractive index (which is unitless) of the respective medium.