Two polarising filters are positioned adjacent to one another with their planes aligned parallel. The transmission axis of the first polarising filter is inclined at $50^{\circ}$ to the vertical. The transmission axis of the second polarising filter is inclined at $20^{\circ}$ to the vertical. The separation angle between the transmission axes of the two polarising filters is $30^{\circ}$. A beam of vertically polarised light with intensity $8.0\,\text{W m}^{-2}$ falls normally on the first polarising filter. What is the intensity of the light emerging from the second polarising filter?
- Azero
- B$2.5\,\text{W m}^{-2}$
- C$2.9\,\text{W m}^{-2}$
- D$6.0\,\text{W m}^{-2}$