Polarization

=Polarization! =  Polarization occurs when light travels through a polarized lens. As light travels through the lens, its intensity is reduced. The ability of polarization has been used as a way to block some light, from entering certain areas, but it still allows some light to enter. For instance, when a person wears sunglasses, their eyes are protected from the sunlight, but yet the light is not completely blocked off otherwise, they would be unable to see anything at all.

The usage of multiple polarized lenses has another effect on light as well. When more polarized lenses are used, the amount of light that is blocked increases. If the polarization amount of light allowed through a polarizer was measured and graphed, the graph would be sinusoidal with maximum and minimum points at 90 degree intervals.

If only one polarizer is used at the amount of light allowed through is always going to be cut in half. Therefore only 50% will actually hit the sensor.

But why 50%? Ordinary light consists of waves whose electric fields are randomly oriented in all lateral directions. We would said there is vertical component and horizontal component. Thus when the filter is in horizontal, the vertical lights are blocked and the horizontal ones pass through. After this process, the light is said to be polarized. And by using the above equation, we can get the light passing through is 50%. When another polarizer is added at 180 degrees from the original, it is determined that 50% of the light will reach the sensor. The light intensity is same compared to the first one. It is because the light that pass through the first filter are all horizontal one. The second filter is horizontal too. So no light is block when they pass through the second one since all vertical ones are block at the beginning.

If the second polarizer is placed 90 degrees away from polarizer 1, 0% of the light will reach the sensor, which means that all of the light is blocked of. When the transmission axises of two filters are in perpendicular, both vertical and horizontal component of light is blocked. Thus no light pass through. If the two polarizers are at an interval of 45 degrees apart from each other the amount of light allowed through will be relatively 25%. We know how to find out the intensity of polarized light if the angle is 90 or 180. But how about angle like 45 or others? To find the intensity of the polarized for any angle, the following equation is needed. Take the experiment data above.

For the following graph, the relationship between the light that is read by the monitor to the angle measurement of the second polarizer. For the graph, the first polarizer is at 180 degrees. As you can tell, the relationship between the angle of polarizer 2 and the light that is allowed through is sinusoidal. As the angle of the second polarizer move towards angle 90, 270, 450 ... polarizer 2 and polarizer 1 is more perpendicular to each other, that's why the light emitted decrease. As the angle of the second polarizer move towards angle 0,180, 360, 540 ... polarizer 2 and polarizer 1 is more parallel to each other, that's why the light emitted increase. The amplitude is 50% because half of the light is blocked due to the first polarizer.

-Steve W. and Tommy Z.