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