Solving Thin-Film Problem with Wavelengths 690 and 575nm

• judonight
In summary, the problem involves a film floating in water with indices of 1.25 and 1.33, respectively. The observed wavelengths are 690 and 575nm. The phase is shifted by pi and the question is asking for the thickness of the film. The solution may involve the equations for interference and constructive interference, using the given wavelengths and indices.
judonight
Problem states: Wavelengths of 690 and 575nm are observed when white light is directed on a film floating in water. The index of the film is 1.25, and the index of water is 1.33.

What is the thichkness?

I know the phase is shifted by pi., but other than that I am not sure where to go with this problem!

Can I get a nudge in the right direction?

Thanks

--k

I suppose I am only searching for the equation used to determine the answer.

I think that for thin films which have an index of refraction higher than the water, the thickness is wavelength over 4... but, for the situation of having an index lower than that of the water, I presume that some light makes it to/through the water...

Any help would be greatly appreciated!

Some light does make it through, even if the index is higher. But they're not asking about the amount of light transmitted or reflected - what they are giving you are the wavelengths where the reflection is a maximum. What is the name of chapter you working on now - interference? You have constructive interference at both wavelengths, which implies something about the thickness of the film - so you should be able to set up 2 equations relating wavelength, thickness and optical path difference between waves reflecting off the front and back surfaces of the film.

1. How do wavelengths of 690nm and 575nm help solve thin-film problems?

The wavelengths of 690nm and 575nm are within the visible light spectrum and are commonly used in thin-film interference experiments. These specific wavelengths correspond to red and green light, which are easily distinguishable by the human eye. By using these wavelengths, scientists can accurately measure the thickness of thin films and determine the refractive index of the material.

2. What is the thin-film problem and why is it important to solve?

The thin-film problem refers to the interference patterns that occur when light waves reflect off of multiple layers of thin films. This can create undesirable effects such as reduced visibility or distortion of colors. It is important to solve this problem in order to accurately measure and control the properties of thin films, which are used in various industries such as optics, electronics, and coatings.

3. How do scientists use the wavelengths of 690nm and 575nm to solve thin-film problems?

Scientists use these specific wavelengths to create interference patterns with thin films. By adjusting the thickness of the films, the intensity and color of the interference pattern changes. By measuring and analyzing these changes, scientists can determine the thickness and refractive index of the thin film, allowing them to solve the thin-film problem.

4. Are there any limitations to using wavelengths of 690nm and 575nm for solving thin-film problems?

One limitation is that these wavelengths are only suitable for measuring thin films with a certain range of thickness. If the film is too thin, the interference patterns may not be visible or measurable. Additionally, if the film is too thick, the interference patterns may become too complex to accurately analyze. In these cases, other wavelengths or techniques may be necessary.

5. Can wavelengths other than 690nm and 575nm be used to solve thin-film problems?

Yes, scientists have used various other wavelengths within the visible light spectrum, as well as other parts of the electromagnetic spectrum, to solve thin-film problems. Each wavelength has its own advantages and limitations, and the choice of wavelength depends on the specific properties and thickness of the thin film being studied.

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