Light — practice question

Light moves from air into glass. How are the refractive index $n$ of the glass, the angle of incidence $i$ and the angle of refraction $r$ related?

• A$n = \frac{i}{r}$
• B$n = \frac{r}{i}$
• C$n = \frac{\sin i}{\sin r}$
• D$n = \frac{\sin r}{\sin i}$