# Interference patterns in thin films

• haha1234
In summary, the conversation discusses the phenomenon of interference patterns in thin films and their role in determining the diameter of a fiber. The investigator has provided a fiber as evidence and the technician is attempting to measure its diameter using interference bands observed between two glass plates. The question of how to measure the diameter in the case of destructive interference is raised, but it is noted that this is a homework question and the individual is advised to research and discuss their findings rather than expect a direct answer.
haha1234
Why the interference patterns are separated when there are many light beams transmit through the film?

Thanks!

There are multiple reflections between all of the interfaces. What emerges will be the sum of all these.
What do you mean, in this context, by the word "separated"?

Yes, I think you need to explain your question more clearly. I too cannot understand what you are asking.

This is the question

An investigator finds a fiber at a crime scene that he wishes to use as evidence against a suspect. He gives the fiber to a technician to test the properties of the fiber. To measure the diameter d of the fiber, the technician places it between two flat glass plates at their ends as in the figure below. When the plates, of length 15.0 cm, are illuminated from above with light of wavelength 610 nm, she observes interference bands separated by 0.555 mm. What is the diameter of the fiber?

I don't know why there are interference patterns separating,and I want to know if destructive interference occurs,how to measure the diameter of the fibre?

This is clearly a homework question. It should be in the Homework section at the very top of the index.

You cannot expect a simple answer for this sort of question on PF. You need to demonstrate that you have actually tried for an answer on your own. Say what you have found out so far and what you think about it. We do not spoon feed students. The topics of thin film interference and Newton's Rings will be thrown up in hundreds of hits on Google. Read what Wiki has to say about it and then come back to discuss it.

## What are interference patterns in thin films?

Interference patterns in thin films occur when light waves interact with a thin layer of material, such as a soap bubble or a thin film of oil on water. The light waves are reflected and refracted at different angles, resulting in a pattern of light and dark areas.

## What causes interference patterns in thin films?

Interference patterns in thin films are caused by the superposition of light waves that are reflected and refracted at different interfaces within the thin film. This creates areas of constructive and destructive interference, resulting in the observed pattern.

## How are interference patterns in thin films used in scientific research?

Interference patterns in thin films are used in a variety of scientific research, including studies on the properties of light, the behavior of thin films, and the composition of materials. They are also commonly used in optical instruments, such as microscopes and spectrometers.

## What factors affect interference patterns in thin films?

The thickness and refractive index of the thin film, as well as the angle of incidence and the wavelength of the light, can all affect the interference patterns observed. Other factors, such as the temperature and composition of the material, may also play a role.

## Can interference patterns in thin films be used for practical applications?

Yes, interference patterns in thin films have a variety of practical applications, including in anti-reflective coatings, optical filters, and thin film solar cells. They are also used in the production of certain types of electronic displays and in the analysis of thin film materials.

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