PURPOSE: To demonstrate explicitly that the angle of rotation of polarized light in an optically active medium is a function of wavelength.
DESCRIPTION: The prism spectrum part of the experiment consists of a bright point source with condenser lens and iris, a 10 cm focal length cylindrical convex lens which focuses light onto a slit, and a 15 cm focal length lens which focuses the light passing through a prism onto a distant screen. After the spectrum is aligned, the optical activity arrangement, consisting of a uniform plastic cylinder of Karo syrup between two rotatable polaroids, can be installed between the 15 cm lens and the prism, as seen in the photograph. As either polaroid is rotated a dark band moves through the spectrum, because the polaroid absorbs the color/wavelength that has rotated by that angle.
REFERENCES: (PIRA unknown.)
EQUIPMENT: Bright point source with condenser lens and iris, 10cm focal length cylindrical convex lens, slit, 15cm focal length convex lens, rotating polaroid, plastic cylinder of Karo syrup, rotating polaroid, and equilateral prism.
SETUP TIME: 10 min.
Go back to Lecture-Demonstration Home Page.