16.3 Laws of Refraction at Plane Surfaces, Refractive Index
The ray of light bends towards (away from) the normal when
it enters from rarer to denser (denser to rarer) medium. This bending of length
is called refraction.
The laws of refraction are :
(i) Incident ray (IP) & Refracted ray (PR) lie on either
side of the normal (MPN') to the boundary of separation.
(ii) IP, NPN' & PR lie on the same plane which is called
the plane of incidence.
(iii) i (angle of incidence) > r (angle of refraction),
when the light enters from rarer to denser medium and
i' < r' for the converse case.
(iv) Sine of i bears constant ratio to sine of r for the given
pair. The constant is called the refractive index of medium 2, with respect
to medium 1.