Physics - Wave Optics Question with Solution | TestHub

Initial intensity of unpolarized light from the source is $I_0$.

After passing through the first polaroid $P_1$, the intensity becomes $I_1=\frac{I_0}{2}$.

The angle between the pass axes of $P_1$ and $P_2$ is ${\theta }_1=60^{\circ }$. By Malus's law, the intensity after passing through $P_2$ is $I_2=I_1{\cos }^2{\theta }_1=\frac{I_0}{2}{\cos }^{2}60^{\circ }$.

The pass axis of $P_3$ is at an angle of $90^{\circ }$ with respect to $P_1$. The angle between the pass axes of $P_2$ and $P_3$ is ${\theta }_2=90^{\circ }-60^{\circ }=30^{\circ }$.

The intensity after passing through $P_3$ is $I_3=I_2{\cos }^2{\theta }_2=\frac{I_0}{2}{\cos }^{2}60^{\circ }{\cos }^{2}30^{\circ }$.

Answer: $\frac{I_0}{2}{\cos }^{2}60^{\circ }{\cos }^{2}30^{\circ }$