Which of the following correctly describes Snell's law of refraction?
1
Ratio of sine of angle of incidence to sine of angle of refraction is a constant
2
Ratio of cosine of angle of incidence to sine of angle of refraction is a constant
3
Ratio of tangent of angle of refraction to tangent of angle of incidence is a constant
4
Ratio of sine of angle of refraction to the sine of angle of refraction is a constant