PURPOSE: Demonstrate absorption spectrum of chlorophyll.

DESCRIPTION: A bright point source with condenser lens and iris is focused by a 20 cm focal length cylindrical convex lens onto a slit, which is in turn focused onto a distant screen by a 20 cm focal length spherical convex lens. A white light spectrum is obtained by inserting an equilateral prism just after the spherical lens. A chlorophyll solution, prepared by smushing up grass in a container of methanol, is placed in the beam just before the slit. The system now shows the absorption spectrum of chlorophyll.

The color of chlorophyll is not a narrow band of green, but rather is achieved by removing the complementary color, magenta, through absorbing some of the red and much of the blue components. The absorption spectrum of chlorophyl is compared with the full spectrum of white light below.

SUGGESTIONS:

REFERENCES: (PIRA 6F10.56)

EQUIPMENT: Bright point source with condenser lens and iris, 20cm focal length cylindrical convex lens, slit, 20cm spherical convex lens, and prism, with solution of smushed grass in alcohol.

SETUP TIME: 10 min.