I've been doing some working with a michelson interferometer, specifically finding the refractive index of a glass block. I am given this eqn:(adsbygoogle = window.adsbygoogle || []).push({});

n = (2t-ML)(1-cos)/ (2t (1 - cos) - mL)

Where n is the refractive index of the glass

M is number of fringes passing

I have left the thetas out becuase they mess up how it looks but u can assume cos = cos theta1.

t is thickness of the glass

L is Lambda the wavelength of the light.

I am trying to prove this eqn.

Here is what I have.

I know that the optical path length is the distance the light travels in the glass * n.

Where B is the distance travelled in the glass B = t cos theta2

Theta1 is angle of incidence, theta 2 is angle of refraction.

From elsewhere L = 2d/M

In this case B will be my d as this is the distance that the beam travel in excess of its normal path.

Now I have tried just shoving everything in and hoping I can simplify it but to no avail. How should I be going about this?

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# Homework Help: Simple Interferometer question

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