A beam of light moving 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 shows this ray of light before it enters the block and after it enters the block. 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$5.0 \times 10^8\,\text{m s}^{-1}$