Experiment 13: Polarization of Light

Introduction: The purpose of this experiment is to witness the polarizing of light and its effect. This is achieved by observing light through a number of polarizing filters and collecting data.

Preliminary Questions:

1) When the polarizing filters are perpendicular to each other, no light is able to pass through. It looks black

2) This is a graph of light intensity versus Rotation angle from 0 to 180 degrees

Procedure:

We attached two polarizing filters to a meter stick in front of a light source and secured alight sensor to it. The polarizing filters were positioned so the most amount of light would come through and were marked. They were then rotated so the least amount of light would come through and were marked. The brightest angle is referred to as 0º and the darkest as 90º

We then collected data on light intensity versus angle of rotation and rotated the second polarizer 7.5º at a time clockwise until we turned 90º. We then did the same thing counterclockwise.

We then moved the second polarizer out of the way and we adjusted a third polarizer to block out as much light as possible and then replaced the second polarizer at the 0º position. We rotated the second one 7.5º at a time just as in the previous step and generated another graph

We then looked at florescent light through a polarizer and then the reflection from a florescent light on the table

Data and Analysis: 
For the two polarizers

The first graph explains that the polarizer filters out light as a function of angle as a sin pattern. This means as you turn it from parallel, the light becomes less and less intense until tapering off to zero, and then it gradually becomes brighter, then quickly becomes brighter, and then brightness slows its speed until you have turned it 180º. The cos^2 graph vs illumination is linear.

For three polarizers

Our graph does not reflect what should happen. Since the first and last lens are perpendicular to each other, the light should not come out, however the middle lens shifting some of the light emitted from the first lens so all of the light is not blocked by the third lens. This means that 45º should yield the most light because it creates the least similar alignment with either the first or third lens. Towards the end of our graph, this becomes clear.

When looking directly at the florescent lights through the polarizing filter, there is no observable change when the filter is rotated. This is because florescent lights are random emitters of light, meaning that they release light at all orientations. If the rotation cancels one, a new one will replace it. This is not so with the reflection of light. The table is not a perfectly reflective surface so the contours of the table partially orient the light. The polarizing lens is able to block light of the specific orientation so when rotated, the reflection of the light will darken.