A beam of polarised light with intensity $I$ falls normally on a polarising filter. The intensity of the transmitted light is $I$. The filter is then rotated about the normal axis through an angle $\theta$. The transmitted light now has intensity $0.75I$. What is the angle $\theta$?
- A$30^\circ$
- B$42^\circ$
- C$49^\circ$
- D$60^\circ$