Which of the following options correctly represents Snell's law of refraction?

According to snell's law of refraction, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given colour of light and a given pair of media.

$\frac{\sin \mathrm{i}}{\sin \mathrm{r}}=\mathrm{constant}$

This constant value is referred to as the refractive index of the second medium with respect to the first.