Optics Question 51
Question: Assertion : 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 : The reflection is Newton’s ring cases will be from a denser to a rarer medium and the two interfering rays are reflected under similar conditions.
[AIIMS 1998]
Options:
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason both are false.
E) If assertion is false but reason is true.
Show Answer
Answer:
Correct Answer: A
Solution:
The central spot of Newton’s rings is dark when the medium between plano convex lens and plane glass is rarer than the medium of lens 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.
