A plane-polarised wave of amplitude $A$ is directed normally onto a polarising filter. The transmission axis of the filter is at angle $\theta$ to the plane of polarisation of the incident wave. What is the amplitude of the wave that emerges from the filter?
- A$A\cos\theta$
- B$A\cos^2\theta$
- C$A^2\cos\theta$
- D$A^2\cos^2\theta$