Physics AP - Wavelength of a Laser (#22)

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.  
5. Then using you're a ruler and you eye look through the glass and
   see where the light rays comes out the other side, and draw an
   line there, do this for every 10o marking.  6) After that draw a
   line connecting all the incident rays and emerging rays, that line
   is the refracted ray.
7. Now measure the angle or refraction, which is between the Normal
   and the refracted ray for all the lines.
8. Then calculate the sine of the angle of incidence, and the sine of
   the angle of refraction to find the index of refraction.
9. Once you have found that find the speed of light through the glass
   by using the equation vg=vo/n.

Data:
0123456789012345678901234567890123456789012345678901234567890123456789
Angle of Incident (i) 0°    10°   20°   30°   40°   50°   60°   70°
Angle of Refract. (r) 0°    8°    14.5° 19°   26.5° 31°   36°   39°
Sin (i)               0     .1736 .3420 .5000 .6428 .7660 .8660 .9397
Sin (r)               0     .1392 .2504 .3256 .4462 .5150 .5878 .6293
Index of Refract. (n) 1.435 1.247 1.366 1.536 1.441 1.487 1.473 1.493

vg=vo/n, 3.00x108/1.435 ==> note: 8 is an exponent
vg=2.09x108(m/s)        ==> note: 8 is an exponent

Analysis/Conclusion:
The conclusion I made from this lab is the index of refraction is
pretty constant even when the lines of the emerging rays are off
some.  That is why the index of refraction is no perfectly constant
in this lab, if the emerging ray would have been better the index of
refraction would have been better also.