The diagram illustrates light moving from air into glass. The angles $v$, $w$, $x$ and $y$ are marked. Which equation is used to find the refractive index $n$ of the glass?
- A$n = \frac{\sin v}{\sin y}$
- B$n = \frac{\sin v}{\sin x}$
- C$n = \frac{\sin w}{\sin y}$
- D$n = \frac{\sin w}{\sin x}$