A beam of light moving at $3.0 \times 10^8\,\text{m s}^{-1}$ falls on the surface of a glass block and is refracted as it passes into the block. The diagram shows this ray before it enters the block and after it has entered. 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$5.0 \times 10^8\,\text{m s}^{-1}$