Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics:
Law of Refraction:
First Law:- The incident ray, the refracted ray and the normal to the refracting surface at the point of incidence, all lie in the same plane.
Second Law(Snell’s Law):- The ratio of the sine angle of incidence to the Sine angle of refraction is constant for the two given media. This constant is denoted by ¹μ₂ and is called relative refractive index of medium 2 with respect to medium 1.