Question

A light ray strike an air/water surface at an angle of 46 degrees with respect of the normal. find the angle of refraction when the direction of the ray is from the air to water

Answer 1

The Snell's law says

$$n_i\sin\theta_i=n_r\sin\theta _r$$

Thus

$$\theta_r=\sin^{-1}\left(\frac{n_i}{n_r}\sin\theta_i\right)$$ $$\theta_r=\sin^{-1}\left(\frac{1.00}{1.43}\sin46^\circ\right)=30^\circ$$