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I have read that any kind of artificial light may emit some energy of IR..my question here that how one can make measurements or computation to find the proportion of IR in the spectrum distribution of the sources...As you know for incandescent bulbs,Planck's law helps in this regard,however,for LEDs or fluorescent lamps, I could not find a way to compute the power spectral distribution because I am working on a formula that needs that power of IR.

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  • $\begingroup$ Any kind of energy converting mechanism will, in practice, generate some heat. That's completely inevitable because of the laws of thermodynamics. However, if you do not care about the thermodynamic limitation, and you are only interested in the light that is generated by the actual quantum mechanical effect underlying the source's operation, then you can find sources that will produce essentially no additional IR radiation as a result of their operating principle. Many lasers fall into that category and so does the right kind of (low pressure) fluorescent lamp. $\endgroup$ – CuriousOne Jan 1 '15 at 23:51
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You cannot "compute" the IR component of the spectrum of an LED without knowing its construction. Typically the white color of the LED is the result of phosphors that are excited at higher frequencies, and that emit different colors at lower frequencies. It is possible to create a white LED with virtually no IR emission (maybe just a bit from the heating of the LED). However there's no way to calculate it that I can think of - you could measure it by using an IR filter and a photodiode with known sensitivity curve.

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