Tested Overhead Projection Series Compiled by HUBERT N. ALYEA Princeton University
Dem. 367-PIodic
7. ENERGY
Device modified from that made by Denver Ulery and his pupil, John Schairer, at the U . S . Scienee Pazillion, Seattle, Washington, 196%
D. Light Energy 3. WITH POLARIZED LIGHT (Continued) Dem. 364-Koro
under Stroin in Polorizer
Syrup and Nicotine in Polorizer
T o show: Stress lines in plastic. Special Device, SD-367, Plastic under strain. See Figure. Cut from 5 X 2 X '/&n. Plexiglas, it fits into SD-360 when the plastic is pinched together slightly.
Experiment developed by W . H. Shbaugh. T o show: Dextro- and leva-rotatory solutions. Materials: Polarizer SD-360; half ounce narrowneck, square, clear-glass bottle full of nicotine (ClaH4&); ditto with Karo symp (mixture of sugars). Procedure: Project both bottles simultaneously in the Polarizer. Rotate the analyzing disc clockwise and counterclockwise to extinction points. Observations: The difference in direction and angle of rotation of the two solutions is a t once evident, each bottle becoming invisible a t different settings of the analyzer disc. Karo is dextro- and nicotine is levorotatory. Note: The two samples may be stored in the bottles indefinitely.
Dem. 365-Cellophane
Tope in Polorizer
T o show: Cellophane tape of different thicknesses viewed in polarized light. Materials: Cross and re-cross half a dozen strips of I-in. cellophane tape on a 43/8 in. disc of Plexiglas; Polarizer SD-360. Procedure:
Rotate disc and Polaroid in SD-360.
Observations: Beautiful colored patterns; a 190' rotation brings in the complimentary color a t any one spot.
SD-367.
Plostic under stroin
Procedure: ( a ) Project SD-360 with the SD-367 piece un-strained. (b) Then pinch the ends towards each-other, set in SD-360 and again project. Rotate the Polaroid disc of SD-360. Observations: Strain lines concentrate a t the square corners but flow evenly around rounded corners. If the plastic were strained to the breaking point, the square comers would shatter first. Dem. 368-Doubly-refrocting
Cakife in Polorizer
T o show: Double refraction of calcite. Materials: Three-inch disc of plastic on the center of which is fastened (cement at edges) a 1 X '/%-inchclear crystal of calcite; a 43/8-inch plastic dish across the face of which is anchored (with tape) a very fine wire (No. 32). Polarizer SD-360. Procedure: Slip the two plastic dishes into the Polarizer. Rotate the calcite crystal, also the Polaroid disc.
Dem. 366-Cellophone
T o show: light.
under Stress in Polorizer
Observations: As the birefringent crystal is tuned there will be one position \ h e r e the wire appears as two wires on the screen.
Crumpled cellophane viewed under polarized
Materials: Polarizer SD-360; wrapper from a package of cigarettes.
E. Mechanical Energy Dem. 369-Sfeom
Engine: Heai into Mofion
Procedure: Crumple up the wrapper, insert in SD-360 and project. Turn Polaroid disc.
Device developed by Charles Owens.
Observations: Beautiful colored patterns; a 190" rotation of the disc gives complimentary colors.
T o show: Transformation of beat energy into mechanical energy. Volume 44, Number 3, March 1967
/
A273
