A beam of light travelling at a speed of $3.0 \times 10^8\,\text{m s}^{-1}$ is incident on the surface of a glass block and is refracted as it passes into the block. The diagram illustrates a ray of this light immediately before it enters the block and after it has entered. The angle of incidence is $55^\circ$ and the angle of refraction is $33^\circ$. What is the speed of light in the glass?
- A$1.8 \times 10^8\,\text{m s}^{-1}$
- B$2.0 \times 10^8\,\text{m s}^{-1}$
- C$4.5 \times 10^8\,\text{m s}^{-1}$
- D$5.0 \times 10^8\,\text{m s}^{-1}$