## Introduction: Calculating the Speed of Light Through Hand Sanitizer!

In this project, we will use Snell's Law to our advantage in order to calculate the index of refraction, and thereby the speed of light of through a hand sanitizer medium.

## Step 1: Setup

Set up the optics kit with ray table/bench, laser/light source, and plan-convex tray. If you are not using a kit, you may make do with a protractor. Fill the tray with some of the solution.

## Step 2: Experimenting

Shine the laser through the flat side of the tray, as seen in the previous setup. You should not observe any refraction when shining normal to the flat side. Begin to swivel the plate, and record the incidence angle and refraction angle of at least 2 different incidence angles. Record your results in a table. In this diagram, you cannot see the incidence beam clearly. Due to this, we took the reflected ray from the flat side of the tray. The angle of the reflecting back ray is the same as the incidence angle.

## Step 3: Calculations

Use Snell's law with all of your data points to determine the index of refraction of the solution.

Assume the index of refraction of air to be 1 or 1.003

Snell's Law: [index of refraction of air] * [sin(incidence angle)] = [INDEX OF REFRACTION OF MEDIUM] * [sin(refracted angle)]

Then calculate the mean of these index values.

Use this to determine the speed of light in the medium.

Formula: SPEED OF LIGHT IN MEDIUM = speed of light in vacuum/index of refraction of medium

And congrats! Your done!

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## 3 Comments

Sorry, i did not understand calculations. Could anyone explain that?

Oh, nevermind, i got it :)

All of a sudden there are a lot of Instructables on Optics. I'm going to dust off my "Jenkins and White".

Nice work.

If I remember correctly, the index of refraction equals the tangent of Brewsters angle.