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Wave Optics — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsWave Optics1 Mark
Question
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.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): For best contrast between maxima and minima in the interference pattern of Young's double slit experiment, the intensity of light emerging out of the two slits should be equal.
Reason (R): The intensity of interference pattern is proportional to square of amplitude.
✓

Answer

  1. Both A and R are true but R is NOT the correct explanation of A.
Explanation:

When intensity of light emerging from two slits is equal, the intensity at minima,

$\text{I}_\text{min}=\Big(\sqrt{\text{I}_\text{a}}-\sqrt{\text{I}_\text{b}}\Big)^2=0$, or absolute dark.

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