Physics AP - Index of Refraction of Air (#23)

Background:
The index of refraction (n) is a constant that is equal to the
velocity of the speed of light through air (v0) divided by the
velocity of the speed of light through glass or any other substance
(vg).  This is proven by the use of the Michaelson Interferometer.
The Michaelson Interferometer is made up of an air column/tube, and a
few mirrors.  There is also a pump to take out or put in air in the
air column, and a laser.  The laser shines straight into a mirror
then onto a surface like a wall then the reflection of the laser go
into the tube and then onto the wall.  Depending on the number of
fringes when air is let in or out you can figure out the index of
refraction.

Problem:
To find the index of fraction of air, and devlop an equation for
that.
 
Materials:
Michaelson Interferometer. 

Procedure:
1. Measure the length of the air column.
2. Then suck out all the air out of the air column.
3. Slowly let the air back into the air column.
4. While the air is coming back in count the fringes that appear on
   the wall, these are t he extra wavelenths.
5. Then derive an equation for the index of refraction. 

Data:
Length of the tube = 72cm or 7.2 x 10-³m
Extra wavelengths = 548

Analysis/Conclusion:
The conclusion I made from this lab is the index of refraction in air
is close to the assumed 1.