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I have a reflecting grating from Edmund. A CD. And I scratched a line on some black photo film. An 8.5 x 11 cardboard has the photo film slit mounted in the center.
In a dark room I used a CFL 5000 K bulb as a source about 6 ft from the slit. This provides somewhat parallel rays at the slit. Hand holding either the commercial grating or the CD I could see a dominate red line (fairly narrow), a very muddy yellow wider band and weak, a strong green line not as narrow as the red, and a haze of blue.
A GE dimmable with visually a lower color temperature had about the same lines as the other bulb, but sharper. I could not make a good visual judgement on the relative intensity of the lines.
The problem with using a CD as the grating is the result is curved lines. With a commercial grating the lines are straight. You would also get straight lines with a standard prism.
To make a useful spectrometer you need to do some mechanical work.
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