Thickness of a film given wavelength and phaseshift....

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Discussion Overview

The discussion revolves around calculating the thickness of a thin film given the wavelength of incident light and the phase shift of rays emerging from the film's surfaces. It involves theoretical considerations related to material properties and the behavior of light in different media.

Discussion Character

  • Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant inquires about the method to calculate the film's thickness based on the given wavelength and phase shift.
  • Another participant suggests that knowledge of the film's material parameters is essential and questions if additional assumptions are necessary.
  • A subsequent post confirms that the material parameters are known.
  • Further elaboration includes the relationship between the speed of light in free space and the wavelength, as well as the phase speed and its calculation using the speed of light in different media.
  • It is proposed that the phase shift can be used to determine the time spent in the medium, which can then be used to find the film's thickness.

Areas of Agreement / Disagreement

Participants appear to agree on the importance of material parameters and the relationship between phase shift and thickness calculation, but the discussion does not reach a consensus on the specific method or assumptions required for the calculation.

Contextual Notes

Limitations include the need for clarity on the assumptions regarding the phase shift and the specific material properties that influence the speed of light in the medium.

Marvin94
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A wavelength of incident light on a thin film is given, and also is known how much the rays coming out from the top surfaces are out of phase. How can be the thickness of the film calculate?
 
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Do you know the material parameters of the film?
Phase shift = time to pass through the medium, and speed in the medium is determined by the material parameters. Are there other assumptions that should be made?
 
Material's parameters are also known.
 
Speed of light in free space c, divided by wavelength ##\lambda ## is your free space frequency (cycles per second).
Your phase is the portion of the cycle that has been completed, so phase speed is ##\omega = \frac {2\pi c}{\lambda} ## (radians per second).
Speed of light is also ## \frac{1}{\sqrt{\varepsilon_0 \mu_0} }##
Speed of light through medium is ## \frac{1}{\sqrt{\varepsilon \mu}} ##
So the question is saying: given the phase shift, determine the time spent in the medium. With that time, and the speed of travel through the medium, determine the thickness.
 

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