Calculating Thin Film Thickness Using Interference Patterns

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Homework Help Overview

The problem involves calculating the thickness of a thin film using interference patterns observed in a Michelson interferometer. The film has a specified index of refraction and is causing a shift in the bright fringes of the interference pattern produced by a specific wavelength of light.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply a formula related to bright fringes but questions whether it is the correct one given the context of the problem. They also seek clarification on when to use a different formula for minima.
  • Some participants inquire about the underlying physics processes, specifically regarding the formation of bright fringes and the role of interference.

Discussion Status

The discussion is ongoing, with participants exploring the concepts of interference and the specific conditions that lead to bright fringes. There is a lack of consensus on the correct approach, but questions are being raised that may lead to a deeper understanding of the topic.

Contextual Notes

Participants are navigating the implications of the problem's setup, including the definitions of maxima and minima in the context of thin film interference. The original poster's reference to 'bright fringes' is a focal point for discussion.

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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