Question

when light goes from water (n=1.333) into air (n=1.000), the angle of a fraction is 25.1. What is the angle of incidence

Answer 1

We can find the angle of incidence from the Snell's Law:

$$n_isin\theta_i=n_rsin\theta_r,$$ $$\theta_i=sin^{-1}(\dfrac{n_rsin\theta_r}{n_i}),$$ $$\theta_i=sin^{-1}(\dfrac{1.0\cdot sin25.1^{\circ}}{1.333})=17.6^{\circ}.$$