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M9-22. Half Wave Plate


To show properties of a half-wave plate.


Bright point source with condenser and iris, yellow filter, two polaroids with two quarter-wave plates on insertable mounts between them.


NOTE: The two quarter-wave plates must be moved together to simulate a half-wave plate.

Setup Time

5 minutes.




Light from a bright point source with condenser and iris passes through a yellow filter and two crossed polaroids onto a distant screen. The quarter-wave plate is then positioned between the two crossed polaroids at any angle except 45 degrees with respect to the two crossed polaroids at the angle which produces the greatest illumination on the screen. Remove the plate and cross the polaroids. The half-wave plate is then inserted set at the angle for darkness. The plate is rotated somewhat less than 45 degrees,producing some light. The analyzer must be rotated by twice the angle of the plate r


Wallace A. Hilton, Demonstration Model of Retardation Plates in Polarized Light, AJP 21, 466-467, (1953). J. G. Winans, Demonstration with Half-Wave Plates, AJP 21, 170-179, (1953).