Kelvin in Lighting

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gndrod

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Ca and Wa
The spectral wavelength is a constant 380 nm (UV) that ionizes the mercury in a fluorescent tube that cause a resonant excitation of the rare earth phosphor coatings to produce the various light frequencies of different hues. Each fluorescent rare earth coat color interacts from the same 380 nm wavelength. rbj
 

gar

Senior Member
090929-1222 EST

This reference under "Principles of operation" provides an accurate and concise description. Note: the primary emission wavelengths are 253.7 nm and 185 nm and these are generated by the electron current thru the tube causing ionization of the gas atoms. The resulting UV radiation, from the return of the ionized atom to its stable state, excites the phosphors on the inside of the tube.
http://en.wikipedia.org/wiki/Fluorescent_lamp

Some other interesting references are:

http://webphysics.davidson.edu/Course_Material/Py230L/spectra/spectra.htm

http://members.misty.com/don/spectra.html

http://physics.nist.gov/PhysRefData/contents-atomic.html

http://ioannis.virtualcomposer2000.com/spectroscope/index.html
http://ioannis.virtualcomposer2000.com/spectroscope/Hg.html Difficult to follow.
http://ioannis.virtualcomposer2000.com/spectroscope/various.html Quite interesting.
http://ioannis.virtualcomposer2000.com/spectroscope/phasmaplan.html#colorphotos
http://ioannis.virtualcomposer2000.com/spectroscope/toyspectroscope.html#colorphotos2 Real interesting and you can do it yourself.

http://en.wikipedia.org/wiki/Ultraviolet

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Dnkldorf

Senior Member
I appreciate the information on the fluorescent and Induction lamps.

I didn't understand the theory behind the phosphorus coatings and how it played a role, but now I do, so thanks.

My thoughts on lights were taking me towards something like the plasma lamp theory,(I didn't know this existed) using different gases.
 

gar

Senior Member
090929-1400 EST

Dnkldorf:

All sorts of materials when directly excited radiate various wavelengths. Some of the references I provided will provide illustrations.

If the visible spectrum and the frequencies of emission of various materials interests you, then the one reference for making a toy spectrometer from a CD disk as a diffraction grating, in the transmission mode, should be helpful.
http://ioannis.virtualcomposer2000.com/spectroscope/toyspectroscope.html#colorphotos2

A source of commerical gratings and prisms is:
Edmund Optics www.edmundoptics.com

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gar

Senior Member
090930-1346 EST

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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