L6-38: COMA

PURPOSE: To illustrate coma.

DESCRIPTION: The filament of a bright point source (about 3x6 mm) is focused onto a distant screen using a 20 cm focal length convex spherical lens, producing the image at the right in the upper photograph above for paraxial rays. A plane front-surface mirror is used to direct a bundle of non-paraxial rays through the lens, producing the image at the left above, which displays coma. The large baffle before the large 20cm lens and the iris following the lens limit stray light so that the two images are clearly differentiated.



EQUIPMENT: Bright point source, front-surface plane mirror, light screen with iris, large 20 cm focal length convex lens, and second iris, all on optical rail rolling table.

SETUP TIME: 5 min.

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