I have a question about light. I am a grad student in chemistry but it has been a very long time since I took physics. In one of the instruments I regularly use (fluorometer), the light that is detected is always also present at double that wavelength. Can anyone explain why this is? It was explained to me as "oh, it's a physical property of light." Is there more to the explanation than that?

Question

aaronq · Answer

I think it's a property of the diffraction grating used

google this: instrumentation for fluorescence spectroscopy

click on the springer link and read the monochromator section

anonymous · Answer

Yes I think you're right. It says "The emission
spectrum from a turbid solution can have a peak at twice the
excitation wavelength due to 2nd-order transmission
through the emission monochromator."

Thanks!

aaronq · Answer

no problem !