Light Polarization
Description of the Experiment
This experiment allows to measure cross-polarization result of light. Two polarizers with variable angle are used in series over a white LED and the light intensity measured.
Light can be described as an electromagnetic wave with a property called polarization due to the electric field oscillation in the plane orthogonal to the propagation direction. When the oscillation is just over a single direction the light is said to be polarized. Certain materials have the property to block the wave except along this precise direction. The objective of this experiment is to reveal how this occur regarding the light intensity.
Links
- Video: rtsp://elabmc.ist.utl.pt:554/polaroide.sdp
- Laboratory: Intermediate e-lab.ist.eu
- Control Room: Polaroide
- Grade: **
Experimental Apparatus
The apparatus consists on a light source (high bright white LED) passing a collimator which focuses the light rays into a parallel beam of light. At the beginning of the optical path it can can be interposed a vertical light polariser.
In the optical path light travel thought two polarized lenses without graduation whose angle of one of them is pre-set and the other is free to rotate around the axis of propagation.
The light is finally collected through a converging lens into a photo-diode that measures the incident radiation intensity. This intensity is obviously the result of attenuation introduced by polarizing systems brought in its optical path.
Protocol
In this control room we can measure the attenuation of a light beam caused by the cross-rotation of two polarises lenses. This beam can be selected from the light source or can be previously polarized.
The supervisor of the experiment can choose two sweep limits for one polarizer and set the angle of the second polarizer acquiring the value of the transmitted power in a photo-diode.
The resolution (angle increment between two samples) can be chosen according to the interest of the control room supervisor.
