PURPOSE: To show the emission line spectrum for various low pressure gases, an absorption line spectrum from Na, and a continous spectrum from diffracted white light.
DESCRIPTION: To show emission lines, various gas spectrum tubes of He, H2, Na and Xe are diffracted through a grating. The diffracted image of the lines is focused with a camera and projected to the class.
To show emission lines, a white light is projected through a sodium flame. The sodium flame selectively absorbs the portions of the white light that are in the narrow parts of the sodium spectrum. The image is diffracted with a grating, and the diffracted image of the absorption lines is focused with a camera and projected to the class, as shown in the above photo at right.
To show a continous spectrum, a white light source is diffracted with with a grating. The diffracted image of the continous spectrum is focused with a camera and projected to the class.
EQUIPMENT: Gas discharge tubes, white light source, gratings, camera, soudium flames with projector.
SETUP NOTES: Note that the absorption lines using the sodium flame can only be
performed in the basement lecture halls where gas lines are supplied. To show this
on the first floor the high pressure discharge Na lamp must be used, as shown below.
This is a very bright spectral source which shows bright absorption and emission
lines as well as a continuous spectrum.
High Pressure Sodium Lamp
Updated by Jun Qi in 3/20/2000