PURPOSE: Show colors of additive filters along with their spectra.

DESCRIPTION: Two sets of red, green and blue additive color filters are used to simultaneously observe the color of the filter and its spectrum. A baffle placed on an overhead projector has a cutout into which the the filter is placed to show the color of the filter. The prism spectrum setup of demonstration N1-01: PRISMATIC SPECTRUM OF WHITE LIGHT - POINT SOURCE is used with the filter placed in a holder just before the slit. The color of the light passed by the filter on the overhead projector is located on the screen adjacent to the spectrum for easy comparison.

Positive color filters are seen to pass a band of wavelengths around their apparent color, as seen in the photographs above.

SUGGESTIONS: See Question of the Week #192 for suggestions on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 6F10.50)

EQUIPMENT: Bright point source with condenser lens and iris, 20cm focal length cylindrical convex lens, slit, 20cm spherical convex lens, and flint glass prism, with red, green and blue positive color filters and overhead projector with baffle.

SETUP TIME: 5 min.