Calculating Thin Film Thickness Using Interference Patterns

AI Thread Summary
The discussion revolves around calculating the thickness of a thin film using interference patterns in a Michelson interferometer. Given a film with a refractive index of 1.60 and a shift of 8 bright fringes with light of wavelength 580 nm, the calculated thickness is 1.5 µm. The user seeks confirmation on the application of the formula for bright fringes and clarification on the conditions for using the formula for minima. The physics involved includes the principles of interference and how bright fringes are formed. Overall, the focus is on ensuring the correct application of formulas in thin film interference problems.
Jimbob999
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Homework Statement


A thin film with an index of refraction of 1.60 is placed in one of the beams of a Michelson interferometer. If this causes a shift of 8 bright fringes in the pattern produced by light of wavelength 580 nm, what is the thickness of the film?1.5 µm
2.9 µm
3.9 µm
7.7 µm
16 µm

Homework Equations



2L = (m + 1/2) lambda/n2 (maxima - bright film in air)

The Attempt at a Solution


[/B]
2L = 8.5 (5.7x10^-7 / 1.6)

L = 1.5µm

I am just trying to find out whether I used the right formula here, as it states in the question 'bright fringes', so I am assuming that bright film in air formula applies.
Also how would I know to use the other formula for minima?

Thanks.
 
Physics news on Phys.org
What physics process is at work in this problem?
How do bright fringes come about?
 
Last edited:
andrevdh said:
What physics process is at work in this problem?
How do bright fringes come about?
Intereference, Interference?

But that doesn't really get me anywhere...
 
Anyone can help?
 

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