# Index of refraction of the material

## Homework Statement

A laser is fired into a wet paper placed ontop of a glass plate of thickness $d$ and an angle of $0$ degrees. When the light hits the paper and goes through the plate it forms a circle of light of radius $R$. What is the index of refraction of the glass plate?

## Homework Equations

3. The Attempt at a Solution [/B]
Apperently the answer is $\frac{\sqrt{R^2+d^2}}{R}$. When the light hits the paper it bursts kind if...and forms a cone which base is the circle formed at the end but how was this proportion made. Its the $\frac{1}{sinx}$ where $sinx$ is the sine of te entry angle

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Twigg
Gold Member
Hint: Paper is white because it scatters light evenly in the visible. I'm fairly sure the mechanism is Rayleigh scattering (paper is just wood pulp after all, so diffuse fibers, either that or its because of the absorbed water molecules being suspended in low density, I'm honestly not sure which but it doesn't affect the solution). The scattered light is reradiated in different directions. How much of this light is totally internally reflected?

Cool problem!!! Does anyone know why the paper has to be wet for it to work?

Hint: Paper is white because it scatters light evenly in the visible. I'm fairly sure the mechanism is Rayleigh scattering (paper is just wood pulp after all, so diffuse fibers, either that or its because of the absorbed water molecules being suspended in low density, I'm honestly not sure which but it doesn't affect the solution). The scattered light is reradiated in different directions. How much of this light is totally internally reflected?

Cool problem!!! Does anyone know why the paper has to be wet for it to work?
We need to advertise this problem xD

haruspex
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