Question

Unpolarised light is passed through a polaroid $P_1$.When this polarised beam passes through another polaroid $P_2$ and if the pass axis of $P_2$ makes angle $\theta$ with the pass axis of $P_1$. then write the intensity when $\theta$ varies from $0to2\pi$.

Answer 1

The intensity of light when passed through different Polaroid is,

$I_1=\frac{I_0}{2}........\left(i\right)I_2=\frac{I_0}{2}{\cos }^2\left(\alpha \right)......\left(ii\right)I_3=\left(\frac{I_0}{2}{\cos }^2\right(\alpha \left)\right){\cos }^2\left(\beta \right)..........\left(iii\right)$

Now,

$\frac{I_0}{2}=\frac{I_0}{2}{\cos }^2\left(\alpha \right)$ since ($I_1=I_2$)

$\Rightarrow {\cos }^2\left(\alpha \right)=1or,\alpha =0$

Similarly, $\beta =0$