Solving Thin Film Problem: Wavelength in Visible Spectrum

In summary, the conversation discusses a problem with determining the correct wavelength in the visible spectrum that is most strongly transmitted through a thin film of magnesium fluoride with a thickness of 80.0 nm on a camera lens. The formula 2t= m*(lambda) is being used but has resulted in incorrect answers. The key to solving the problem is understanding the index of refraction of the MgF2. The goal is to achieve destructive interference for reflection at the first surface.
  • #1
wsuask
2
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A camera lens (n = 1.80) is coated with a thin film of magnesium fluoride (n = 1.45) of thickness 80.0 nm. What wavelength in the visible spectrum is most strongly transmitted through the film?

I have tried to solve this problem for quite a while now, and i hate to admit that there might be a small thing that i am missing. i have reached the following answers : 116 nm, 160 nm and 232 nm and all of them are wrong. I am using this formula: 2t= m*(lambda). I only have 2 tries left so please help me out. Also include a reason why you reached that answer. I have a final comming up and i would love to learn the propper way to do this. Thank you in advance.
 
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  • #2
You want destructive interference for reflection at the first surface.
I think this means lambda in the glass=t.
 
  • #3
...

Thanks for your attempt, but I already figured out the correct way of doing it. The index of refraction of the MgF2 is the key to the answer.
 

1. What is a thin film?

A thin film is a layer of a material that has a thickness on the order of nanometers to micrometers. It can be deposited on a surface using a variety of techniques, such as physical vapor deposition or chemical vapor deposition. Thin films are commonly used in various applications, including optical coatings, electronics, and solar cells.

2. What is the visible spectrum?

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. It includes wavelengths of light that range from approximately 400 to 700 nanometers, corresponding to the colors of the rainbow: violet, blue, green, yellow, orange, and red.

3. How does light interact with a thin film?

When light strikes a thin film, some of it is reflected from the surface, while some of it enters the film. As the light travels through the film, it interacts with the material and can be reflected, transmitted, or absorbed. The behavior of light in a thin film depends on the thickness of the film and the properties of the material.

4. Why is the wavelength of light important in thin film problems?

The wavelength of light is important in thin film problems because it determines how the light will interact with the film. The thickness of the film and the wavelength of light must be in a specific relationship for certain interference effects to occur, such as constructive or destructive interference. This relationship is known as the phase difference and is crucial in solving thin film problems.

5. What are some common techniques for solving thin film problems?

Some common techniques for solving thin film problems include the Fresnel equations, the transfer matrix method, and the optical path difference method. These methods involve using the properties of light and the characteristics of the thin film to determine the phase difference and ultimately the wavelength of light in the visible spectrum. Other techniques, such as ellipsometry and interferometry, can also be used to measure the thickness and refractive index of thin films.

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