MadSci Network: Physics

Re: Why does glass glow orange when a green laser passes through it ?

Date: Mon May 7 11:47:10 2001
Posted By: Tom Roltsch, Staff, Physics, Raven,Inc
Area of science: Physics
ID: 987240710.Ph

There are two possibilities. Number one is that the laser is not really a 
single line, but there is a faint orange-yellow line present as well. As 
the laser light passes through the glass the longer wavelengths are 
refracted more than the shorter wavelengths and thus become separated from 
the beam. You can test this by passing the beam through a diffraction 
grating. The grating will split up the beam into its component parts. You 
could also try a prism, but the grating will work better. The second, 
less  likely, possibility is that you are seeing fluorescence. The glass 
atoms are absorbing the laser photons then re-emitting photons at a longer 
wavelength. Usually this will not occur in optically pure glass, but 
rather it happens in glass that contains some impurities or dye. My guess 
is that you are seeing the orange-yellow line that is already present in 
the beam. Argon lasers emit at least four colors of visible light, but the 
green-blue color is by far the brightest. With a grating you should be 
able to see violet, blue, blue-green, and orange-yellow light. Good luck!

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