JEE Main · 2025 · 03 Apr 2025 · Shift 2 · Wave Optics

Two monochromatic light beams have intensities in the ratio

1 : 9

. An interference pattern is obtained by these beams. The ratio of the intensities of maximum to minimum is

(A) $8 : 1$
(B) $9 : 1$
(C) $3 : 1$
(D) $4 : 1$ ✓ Correct

Answer: (D)

Solution

For two beams of intensities

I_{1}

and

I_{2}

, the extremes are

I_{m a x} = (I_{1} + I_{2})^{2}

and

I_{m i n} = (I_{1} - I_{2})^{2}

. With

I_{1} : I_{2} = 1 : 9

the amplitudes are in the ratio

1 : 3

, so

I_{m a x} \propto (1 + 3)^{2} = 16

and

I_{m i n} \propto (3 - 1)^{2} = 4

. The ratio of maximum to minimum intensity is

4 : 1

JEE Main · 2025 · 03 Apr 2025 · Shift 2 · Single correct option

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