Spectroscopy
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When we look through a spectoscope at daylight, we see a continuous rainbow of colour, but then to the right, also a black part and then a bright lilac line. Please can you tell me what this is?
Peter writes ...
A diffraction grating produces not one spectrum but several. You normally see the first order spectrum. However there is a second order spectrum further round and we think that you are probably seeing the blue/violet end of the second order spectrum.
Look at the spectra produced by a CD Rom when the shiny side with the tracks reflects white light. Gradually tilt the CD and you will see the multiple spectra at different angles.
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updated: 08 December 2003
