When plane-polarised light with amplitude $A$ is sent through a polarising filter as illustrated, the emerging light has amplitude $A \cos \theta$. The intensity of the incident beam is $I$. What is the intensity of the light emerging when $\theta$ is $60.0^\circ$?
- A$0.250\,I$
- B$0.500\,I$
- C$0.750\,I$
- D$0.866\,I$