Polarization of Light

Objective
The purpose of this experiment is to observe the light intensity through polarizing filters and measure the changing intensity as a function of angle between the axes. 

Pre- lab question
1. The light intensity is decreasing and at 90 degree it will dark, which means the light can not though the filter.
2. The light intensity is decreasing until it becomes dark and then starts increasing to become very bright.

Experiment

polarizing filters

 

Two polarizing filters. at 90 degree got dark

set up the three polarizing filters 

From this picture, we can see the light pass though the first filter, we get stright light,  the light get darker and darker, but the 45 degree is the maximum

 Data



graph 1




Three polarizers:








The center of axis of the first polarizer is 0 and 90 for the third polarizers. If the second polarizer is on its 0 or 90, the light intensity will be the minimum. If the second polarizer is at 45 orientation, then the intensity observed will be the maximum.

I0*cos(theta)^2*cos(pi/2- theta)^2



I0*cos(theta)^2*sin(theta)^2

1/4 I0*sin(2*theta)^2

when theta= 45, it reaches the maximum value.

 

 

Conclusion:
In part one, when the first polarizer is set to 0 degree and the second polarizer is perpendicular to the first one, the intensity of light will be minimum if the third polarizer is perpendicular to the second one. But if the second one moves to 45 degree, the intensity of light will be maximum. Light intensity depends on the angle of polarization. The light intensity is maximum or minimum as long as polarization is parallel or perpendicular. 

In part two, based on the same reason, first one at 0, second and third are 45 degree. that is the maximum.