sinisinr\frac{\sin i}{\sin r}sinrsini = velocity in airvelocity in glass\frac{\text{velocity in air}}{\text{velocity in glass}}velocity in glassvelocity in air
sinisin30\frac{\sin i}{\sin 30}sin30sini = 3×1082×108\frac{3 \times 10^{8}}{2 \times 10^{8}}2×1083×108
Sin i = 34\frac{3}{4}43 = 0.75
