Calculating Thin Film Thickness Using Interference Patterns

In summary, the question involves a thin film with an index of refraction of 1.60 being placed in one of the beams of a Michelson interferometer. This causes a shift of 8 bright fringes in the pattern produced by light with a wavelength of 580 nm. To find the thickness of the film, the formula 2L = (m + 1/2)λ/n2 is used, where L is the thickness of the film, m is the number of fringes, λ is the wavelength of light, and n is the index of refraction of the film. Using this formula, the thickness of the film is calculated to be 1.5 µm. Interference is the physics process at
  • #1
Jimbob999
26
2

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.
 
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  • #2
What physics process is at work in this problem?
How do bright fringes come about?
 
Last edited:
  • #3
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...
 
  • #4
Anyone can help?
 

Related to Calculating Thin Film Thickness Using Interference Patterns

1. What is interference from thin films?

Interference from thin films is a phenomenon that occurs when light waves interact with thin films of different materials, resulting in the appearance of colors. This is due to the constructive and destructive interference of the light waves as they reflect off the surfaces of the thin film.

2. How does the thickness of the thin film affect interference?

The thickness of the thin film plays a crucial role in interference. Thicker films will result in more pronounced interference patterns, while thinner films will produce more subtle color changes. In general, as the thickness of the film increases, the number of interference fringes also increases.

3. What factors determine the colors observed in interference from thin films?

The colors observed in interference from thin films are determined by the thickness of the film, the wavelength of the incident light, and the refractive indices of the materials involved. These factors interact with each other to produce a unique set of colors for each specific thin film system.

4. Can interference from thin films be observed in everyday life?

Yes, interference from thin films can be observed in everyday life. Some examples include the colorful patterns on soap bubbles, the rainbow colors on oil slicks, and the iridescent colors on the wings of certain insects. It can also be observed in man-made objects such as anti-reflective coatings on glasses and computer screens.

5. How is interference from thin films used in scientific research and technology?

Interference from thin films has various applications in scientific research and technology. It is used in the design of optical coatings for lenses and mirrors, as well as in the production of thin film devices such as solar cells and liquid crystal displays. It is also used in the study of thin film properties and in the analysis of chemical structures through techniques like ellipsometry.

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