Two parallel glass plates of index of refraction n
are separated by an air film of thickness d. Light of wavelength λ
in air, normally incident on the plates, is intensified
on reflection when, for some integer m
If only one ray is π shifted: 2nd=mλ (min), 2nd=(m+1/2)λ (max)
If both rays π shifted: 2nd=mλ (max), 2nd=(m+1/2)λ (min)
The Attempt at a Solution
I've attached a diagram of two different for how I picture light should be transmitted in this problem. I'm not sure which one would be a correct approach.
Going with the first diagram,
This would result in a net π shift, so it's conditions would be 2nd=mλ (min) and 2nd=(m+1/2)λ (max).
I chose answer (B) 2d=mλ/n, since the question asks for "intensity increase" so I am assuming it is asking about the condition for a bright fringe; and also because it's one of the only options that takes the index of refraction (n) into account.
I would just like to verify that my reasoning is correct.