Physics for IGCSE & O level - Rays And Waves (Section 6 - No. 5)
What is Snell's Law?
sin i / sin r = refractive index
sin r / sin i = refractive index
sin i * sin r = refractive index
cos i / cos r = refractive index
Explication
Snell's Law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the refractive index.