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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): Newton's rings are formed in the reflected system. When the space between the lens and the glass plate is filled with a liquid of refractive index greater than that of glass, the central spot of the pattern is dark.
Reason (R): The reflections in Newton's ring cases will be from a denser to a rarer medium and the two interfering rays are reflected under similar conditions.
✓

Answer

  1. Both A and R are true and R is the correct explanation of A.

Explanation:

The central spot of Newton's rings is dark when the medium between piano convex lens and plane glass is rarer than the medium oflens and glass. The central spot is dark because the phase change of $\pi$ is introduced between the rays reflected from surfaces of denser to rarer and rarer to denser media.

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