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Wave Optics

JEE Main level, single correct, medium

18 of 191

Question 18 of 191

In the figure below, $P$ and $Q$ are two equally intense coherent sources emitting radiation of wavelength $20m.$ The separation between $P$ and $Q$ is $5m$ and the phase of $P$ is ahead of that of $Q$ by $90^{\circ}.A,B$ and C are three distinct point of observation, each equidistant from the midpoint of PQ. The intensities of radiation at $A,B,C$ will be in the ratio :

Show answer and solution

Answer: (B) $2:1:0$

\Delta {P}_{A}=\dfrac{\pi }{2}\times \dfrac{20}{2\pi }-5=0\text{so}\Delta {\phi }_{A}=0

\Delta {P}_{B}=\dfrac{\pi }{2}\times \dfrac{20}{2\pi }=5\text{so}\Delta {\phi }_{B}=\dfrac{\pi }{2}

\Delta {P}_{C}=5+5=10\text{so}∆\phi c=\pi

I={locos}^{2}\dfrac{\Delta \phi }{2}

{I}_{A}={I}_{0}

{I}_{B}=\dfrac{{I}_{0}}{2}

\text{Ic}=0

\text{IA}:{I}_{B}:{I}_{C}=2:1:0

JEE Main question paper PDF

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JEE Main 2025 Apr 2 Shift 1 question paper

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