Polarization

  • OP4.1 Cellophane

    This shows wavelength dependence of the polarization of a piece of cellophane--generic scotch tape. This gives an assortment of colors on the vu graph.

  • OP4.2 Iceland Spar (Calcite Crystal)

    There is a plastic model of a calcite crystal that can be used in explain¬ing its properties. Pieces of this crystal are used in conjunction with the overhead to show birifringence. A better demonstration is to place a piece of calcite crystal is placed in a mechanism that rotates in a plane. Striking this crystal with a light source will form two dots on a screen. Rotating the crystal will move one of the dots in a circular pattern around the other.

  • OP4.3 Polaroid

    POLARIZED SHEET. Fill a glass tank with white soap water--not a lot of soap. Place a light source next to the tank. The soap solution polarizes the light so that the polaroid sheet lets the light pass at one angle, but rotated 90° it will stop the light. This is seen on the sides of the tank that are not directly in front of the light. SUNGLASSES. The two polaroid sheet are place together on the overhead. The first sheet polarizes the light and the second either blocks it or lets it pass, depending on its orientation. COSINE SQUARED LAW. This is a piece of polarized plastic that rotates from 0 ° to 90°. Using a light source on a screen, the cosine squared law can be visually seen. REFLECTION. Using the vu graph, a polaroid sheet is placed on the reflected side of the focus lens of the vu graph. This shows that reflected light is polarized.

  • OP4.4 Projection Meter

    This is a plexiglass frame with a fixed polaroid sheet and a rotatable disk of polaroid that is place on the vu graph. There is a photodetector with ammeter that measures the intensity of the light. As the disk is rotated, the meter will measure the change in intensity. The Cosine Law can be measured quantitatively.

  • OP4.5 Stress and Strain Models

    Pieces of plastic are placed in metal brackets between polarizers and braced in place. Using this in the projector will show the stress and strain of the plastic on a projection screen. The pieces are of different shapes and thus produce unique images.