JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Wave Optics

An unpolarized light of certain intensity passes through a combination of two polarizers whose transmission axes are at

3 0^{\circ}

and

9 0^{\circ}

, respectively, with respect to the horizontal axis. A third polarizer with its transmission axis at

6 0^{\circ}

with the horizontal axis is placed between the two existing polarizers. The ratio of the output intensities with and without the third polarizer is ______。

(A) $3/4$
(B) $4/3$
(C) $9/4$ ✓ Correct
(D) $4/9$

Answer: (C)

Solution

Unpolarised light of intensity

I_{0}

leaves the first polariser (axis at

3 0^{\circ}

) as

\frac{I _{0}}{2}

. Without the middle sheet it then meets the

9 0^{\circ}

polariser, whose axis is

6 0^{\circ}

away, giving

\frac{I _{0}}{2} cos^{2} 6 0^{\circ} = \frac{I _{0}}{8}

. With the

6 0^{\circ}

sheet inserted, the intensity after it is

\frac{I _{0}}{2} cos^{2} 3 0^{\circ} = \frac{3 I _{0}}{8}

, and after the final

9 0^{\circ}

polariser (

3 0^{\circ}

further) it is

\frac{3 I _{0}}{8} cos^{2} 3 0^{\circ} = \frac{9 I _{0}}{32}

. The ratio of the outputs with and without the extra sheet is

\frac{9 I _{0} /32}{I _{0} /8} = \frac{9}{4}

JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Single correct option

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JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Wave Optics

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