A horizontal beam of light falls normally on a polarising filter. The incident light is vertically polarised and has an intensity of $24\,\text{W m}^{-2}$. The transmission axis of the filter is inclined at an angle of $30^\circ$ to the vertical. What is the intensity of the light in the transmitted beam?
- A$18\,\text{W m}^{-2}$
- B$21\,\text{W m}^{-2}$
- C$28\,\text{W m}^{-2}$
- D$32\,\text{W m}^{-2}$