I have recently learnt about polarization of light and Malus's Law. Also, I have learnt that a single polaroid allows half of the intensity of light incident on it to pass through (assuming that the incident light was unpolarized).
So if we have two polaroids that are placed with their pass axis at $\theta$ to each other and the intensity of light incident on the first polaroid is $I_o$, then what will the intensity of the emergent light (light emerging from the second polaroid) be?
According to me, the answer should be $\frac{I_o}{2}\cos^2\theta$
Is this correct? Or would it simply be $I_o\cos^2\theta$?
Best Answer
You are correct.
Longer explanation:
When unpolarized light of intensity $I_0$ passes through a Polaroid filter (sometimes referred to as a "polarizer"), it becomes plane-polarized as it passes out of it and its intensity is halved in the process, becoming $\frac{I_0}{2}$.
When this plane-polarized light passes through the second Polaroid filter (sometimes referred to as a "analyzer"), Malus' Law becomes applicable. As the Polaroids' axes are tilted at $\theta$ to each other, the intensity of light after passing through the analyzer becomes $\frac{I_0}{2}\cos^2\theta$ , in accordance with Malus' Law.