MHTCET 13 Apr 2026 Shift 2 Paper

Concept:When unpolarised light passes through a polariser, its intensity becomes half. For each subsequent polariser, Malus’s law applies because the sheets are rotated by $45^\circ$.Explanation:The first polarising sheet reduces the intensity from $I$ to $\frac{I}{2}$.For every following sheet, the angle between adjacent sheets is $45^\circ$.Using Malus’s law, the transmitted intensity is:$$I' = I \cos^2 45^\circ$$Since $\cos 45^\circ = \frac{1}{\sqrt{2}}$, we get:$$\cos^2 45^\circ = \frac{1}{2}$$Thus, every additional sheet reduces the intensity by a factor of $\frac{1}{2}$.If there are $n$ sheets, then after the first sheet the intensity is $\frac{I}{2}$, and the remaining $(n-1)$ sheets each multiply by $\frac{1}{2}$.So, the output intensity is:$$I_{\text{out}} = \frac{I}{2}\left(\frac{1}{2}\right)^{n-1} = \frac{I}{2^n}$$Given $I_{\text{out}} = \frac{I}{64}$, we equate:$$\frac{I}{2^n} = \frac{I}{64}$$Since $64 = 2^6$, comparing the powers gives:$$n = 6$$Answer:$n = 6$Correct option: B.