Diffraction Spectrum Of White Light - Point Source

Purpose

Demonstrate continuous spectrum.

Equipment

Bright point source with condenser lens & iris, 20 cm focal length cylindrical convex lens, precision slit, 10 cm focal length spherical convex lens, & gratings: 2000 lines/inch & 7500 lines/inch.

Setup Time

5 min

Images

n1-11

Description

Light from a bright point source is focused by a condenser lens with iris and a 20 cm focal length cylindrical convex lens onto a slit. The slit is focused onto a distant screen by a 10 cm focal length convex spherical lens. The diffraction grating is placed in the beam following the 10 cm convex lens. The zero order white spot and several spectral orders can be seen on each side of the grating. Gratings of 2000 lines/inch and 7500 lines/inch are available.