The diagram illustrates light travelling from air into glass, with two angles $p$ and $q$ labelled. Which pair of equations may both be used to determine the refractive index $n$ of the glass?
- A$n = \frac{\text{speed of light in air}}{\text{speed of light in glass}},\; n = \frac{\sin p}{\sin q}$
- B$n = \frac{\text{speed of light in glass}}{\text{speed of light in air}},\; n = \frac{\sin p}{\sin q}$
- C$n = \frac{\text{speed of light in air}}{\text{speed of light in glass}},\; n = \frac{\sin q}{\sin p}$
- D$n = \frac{\text{speed of light in glass}}{\text{speed of light in air}},\; n = \frac{\sin q}{\sin p}$