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Laws of Refraction and Refractive Index

Laws of Refraction :
(i) The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.
(ii) When a ray of light undergoes refraction then the ratio of sine of angle of incidence to the sine of angle of refraction is constant.
The Refractive Index : The refractive index of medium 2 with respect to medium is given by the ratio of the speed of light in medium 1 and the speed of light in medium 2. This is usually represented by the symbol n21. This can be expressed in an equation form as

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