Practice portal › Wave Optics › Interference and Young's Double Slit Experiment

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): If Young's double slit experiment is performed in an optically denser medium than air, then the consecutive fringes come closer.
Reason (R): The speed of light reduces in an optically denser medium than air while its frequency does not change.
In the light of the above statements, choose the most appropriate answer from the options given below.

Asked in JEE Main 22nd Jan 1st Shift 2025 · Slabs, media and modified set-ups

• (1) Both (A) and (R) are true and (R) is the correct explanation of (A)
• (2) (A) is true but (R) is false
• (3) (A) is false but (R) is true
• (4) Both (A) and (R) are true but (R) is not the correct explanation of (A)

Step-by-step solution

Why the other options are wrong

• (2) Thinks frequency changes in a medium.
• (3) Thinks the fringes spread out in a denser medium.
• (4) Misses that lower speed at fixed frequency means smaller λ, which is exactly why β decreases.

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