Polarization of Light

Introduction:


This experiment explores the effects of polarizing filters angled with respect to one another on light intensity transmitted.  Selective absorption is the method of polarization for this activity.  Thus, perpendicularly angled filters should theoretically absorb all light that would pass through.  Parallel filters should transmit the most light.  Two filters will be used first and analyzed then three.

Steps:

Two Polarizing filter setup with light source shining through and lumens detector at end.

Example measurement at maximum transmission (theta = 0 degrees)

Data for two polarizers:

degree	intensity	costhetasquared
0	7.432292	0.017037058
7.5	12.07742	0.066987188
15	21.36766	0.146446375
22.5	37.16108	0.249999617
30	54.81256	0.370589943
37.5	85.93489	0.499999337
45	97.54769	0.629408775
52.5	125.883	0.749999234
60	145.857	0.853552687
67.5	175.5858	0.933012149
75	188.1276	0.982962598
82.5	196.9533	1
90	204.3855
97.5	196.0243	0.982963285
105	184.4115	0.933013476
112.5	174.6568	0.853554563
120	142.6054	0.750001532
127.5	106.8379	0.629411338
135	93.36708	0.50000199
142.5	61.78024	0.370592507
150	45.0578	0.250001915
157.5	28.79986	0.146448251
165	19.0451	0.066988514
172.5	7.896804	0.017037745
180	5.10973	7.04E-12

As expected, the plotted data is of cos^2 fit.

Three Polarizing filter:

Three polarizing filter setup.

Illumination vs cos^theta

In the three polarizing filter experiment, we notice that with the first and last filters at 90 degrees with respect to one another, the middle filter must be at 45 degrees to maximize transmission of light.


Conclusion:
Does the light from the fluorescent bulb have any polarization to it? If so, in what plane is the light polarized? How can you tell?

 No, the fluorescent bulb does not have any polarization associated with it.  You can tell this since a single polarizing filter cannot absorb a significant amount of light.  Two are needed.  One to first polarize the light, the other to absorb the polarized light transmitted through.

Does the reflected light have an polarization to it? If so, in what plane is the light polarized? How can you tell?

 Yes, the reflected light has polarization.  A filter may absorb an appreciable amount of the light once angled parallel to the table.

This lab does not lend itself to uncertainty calculations since our logger pro instrument was the only tool used here.  All values are averaged yet they exhibit the trends expected (light intensity if related to the cos^2 of the angle of the polarizing filter.