Wave OpticsHard
Question
Light of wavelength 6000 
is reflected at nearly normal incidence from a soap films of refractive index 1.4. The least thickness of the film that will appear black is :
is reflected at nearly normal incidence from a soap films of refractive index 1.4. The least thickness of the film that will appear black is :Options
A.infinity
B.200
C.2000
D.1000
Solution
Soap film Interference pccure occure between two reflected rays A and B is reflected from upper surface and B is reflected from lower surface.
The path difference between the two becomes 2μt +
If it is equal to
then destructive interference ocdcurs and we see dark fringes fromabove. So the equation 2μt + = give the least value of t for which we see dark fringes.2μt = λ ⇒ t =
≅ 2000 Create a free account to view solution
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