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Wave Optics — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsWave Optics1 Mark
MCQ
For question two statements are given$-$one labelled Assertion $(A)$ and the other labelled Reason $(R).$ Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion $(A):$Two point coherent sources of light $S_1$ and $S_2$ are placed on a line as shown. $P$ and $Q$ are two points on that line. If at point $P$ maximum intensity is observed then maximum intensity should also be observed at $Q.$


Reason $(R):$ In the figure of assertion the distance $\left|S_1 P-S_2 P\right|$ is equal to distance $\left|S_2 Q-S_1 Q\right|$.
  • A
    Both $A$ and $R$ are true and $R$ is the correct explanation of $A.$
  • ✓
    Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$
  • C
    $A$ is true but $R$ is false.
  • D
    $A$ is false and $R$ is also false.
✓

Answer

Correct option: B.
Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$
If maximum intensity is observed at $P$ then for maximum intensity to be also observed at $Q,S_1$ and $S_2$ must have phase difference of $2 \mathrm{~m} \pi ($where m is an integer$)$.

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