Polarization of Light
Polarized Light: General Demonstration
Polarizing sheets are employed to demonstrate polarized light.
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- Two polarizing sheets
- Overhead projector
Polarized light is briefly described and then demonstrated using two overlapping polarizing sheets. The intensity is shown to depend on the relative orientations of the sheets. This is done by holding up the sheets and also by placing them on the overhead projector.
Polarized Light: Stacked Polarizing Sheets
Three polarizing sheets are used to demonstrate the rotation of the polarization plane.
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- Three polarizing sheets
- Overhead projector
- Screen
Two polarizing sheets are oriented 90 degrees with respect to one another and placed on the overhead projector and it is shown that no light gets through. When a third sheet is placed between the two, some light gets through depending on the relative orientation of that third sheet. If the third sheet is removed and placed on top of the first two crossed polarizers, it is observed that no light gets through.
Polarized Light: Optical Activity
Optically active materials are used to demonstrate the rotation of the polarization plane.
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- Two polarizing sheets
- Small separator block
- Overhead projector
- Plastic French curve
- Pieces of cellophane and other plastics
- Screen
Two polarizing sheets separated by a small wooden block are placed on an overhead projector. When various plastic-like transparent materials are placed between the sheets, light of different colors is observed to get through. The colors observed are due to the rotation of the polarization plane which is shown to depend upon the properties of the material, the relative orientation of the polarizing sheets with respect to the material, and the wavelength of the light. It is shown that the observed pattern of light changes when the plastic material is placed under mechanical stress.
Polarized Light: LCD
Light from a liquid crystal display on a hand-held calculator is demonstrated to be polarized.
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- Polarizing sheet
- LCD device (calculator)
A liquid crystal display (LCD) is shown to involve polarized light. This is done by rotating a polarizing sheet in front of the liquid crystal display of a hand-held calculator.
Polarized Light: Laser
Light from a He-Ne laser is demonstrated to be polarized.
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- Laser
- Polarizing sheet
- Screen
A laser beam is directed through a polarizing sheet to a screen. The intensity is shown to vary as the polarizing sheet is rotated.
Polarized Light: Sky Light
Light scattered from the sky is demonstrated to be partially polarized.
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- Polarizing sheet
- Light detector (camera or eye)
A polarizing sheet is placed in front of the recording camera which is directed toward the sky above a nearby mountain. The intensity of the sky light is observed to change as the polarizing sheet is rotated.
Polarized Light: Car Glare
A polarizing sheet is used to diminish the glare from cars in a parking lot.
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- Polarizing sheet
- Light detector (camera or eye)
A polarizing sheet is placed in front of the recording camera which is directed toward the reflected light from several cars in a nearby parking lot. The intensity of the reflected light, especially the glare, is observed to be reduced as the polarizing sheet is rotated.
Interference Simulation Using Polarized Light
A rotating polarizing sheet on the overhead projector is used to simulate the double-slit interference pattern.
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- Polarizing sheets for a double-slit simulator
- Polarizing sheet
- Support frame
- Overhead projector
Two polarizing sheets are prepared with adjacent concentric rings, each with slightly different polarization orientation. When one of these sheets is placed on an overhead projector with a standard polarizing sheet overlayed, the rings appear as concentric circles. As the standard polarizing sheet is rotated, wave motion is simulated. When both polarizing sheets with concentric rings are overlapped and placed on the overhead projector, the double-slit interference pattern is observed. As the standard polarizer is placed between the two sheets and rotated, wave motion from two separate coherent sources is simulated . In this manner, the double-slit interference pattern is demonstrated. The same demonstration is included in the section tiltled Interference and Diffraction .