Assertion: Newton's rings are formed in the r | vedclass

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(A) In the standard Newton's rings experiment,the air film is between the lens $(n_l)$ and the glass plate $(n_g)$,where $n_l > n_{air}$ and $n_g > n_

Vedclass · Accepted Answer

If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

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(A) In the standard Newton's rings experiment,the air film is between the lens $(n_l)$ and the glass plate $(n_g)$,where $n_l > n_{air}$ and $n_g > n_{air}$. The reflection at the bottom surface of the air film occurs at the glass-air interface (denser to rarer),while the top surface reflection occurs at the air-glass interface (rarer to denser). This introduces a phase change of $\pi$ for one ray,resulting in a dark central spot.When the space is filled with a liquid of refractive index $n_{liq} > n_g$,the reflection at the bottom surface occurs at the glass-liquid interface (rarer to denser),and the reflection at the top surface occurs at the liquid-glass interface (denser to rarer). Since both reflections now occur under similar conditions (either both undergo phase change or neither does),the path difference at the center is effectively zero,leading to constructive interference. Thus,the central spot becomes bright. Both the Assertion and the Reason are correct,and the Reason explains why the phase change conditions lead to a bright center.

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