JEE Main 2018 — Wave Optics Question with Solution

As after B intensity of light does not drops, it means both A and B are alligned in single line means their plane of polarization is same.



Let C makes an angle $$\theta$$ with A then C will make $$\theta$$ with B also, as both A and B are alligned in a single line.

So, after C intensity is = $$\frac{\mathrm{I}}{2}$$ cos²$$\theta$$ , and , intensity after B = $$\frac{\mathrm{I}}{2}$$ cos²$$\theta$$ $$\times$$ cos²$$\theta$$

   According to question,

$$\frac{\mathrm{I}}{2}$$ cos⁴$$\theta$$ = $$\frac{\mathrm{I}}{8}$$

$$\Rightarrow$$\,\,\, CO⁴$$\theta$$ = $$\frac{\mathrm{I}}{4}$$

$$\Rightarrow$$ cos$$\theta$$ = $$=\frac{1}{\sqrt{2}}$$ = cos45^o

$$\therefore$$ $$\theta$$ = 45^o