The second law of refraction is also named after its discoverer as :
The Second Law of Refraction is also known as Snell’s Law of Refraction.
As per which the ratio of the sine of the angle of incidence and sine of the angle of refraction is always constant for the light of specific colour and for the pair of given media.
The constant is called refractive index of the second medium in relation to the first medium.
sin isin r=constant