Way to measure wavelength of infrared radiation? 
I am wondering if there is a device for measuring wavelengths of things. As semiconductors emit infrared radiation and I would like to know what is the wavelength it is so I can check to see if its going to be interfering with my project.
Thanks in Advance,
Dean
 A: You probably want to know the amount of light of each different wavelength (a.k.a. light spectrum) the semiconductor is emitting. The device you use for this is a spectrometer or optical spectral analyzer. What semiconductors are you using? Unless you are using an uncommon semiconductor, you can probably find the emission spectrum online.
A: Do you want to know the distribution over a broad range of wavelengths, or do you have a single semiconductor device emitting at a single wavelength that you need to measure? And do you know the approximate wavelength? "Infrared" covers a pretty broad range, from wavelengths that are not-quite-visible to wavelengths that are practically microwaves.
If you have a single source, the best way to measure the wavelength is using interference. If you've got an easy way to see the light, you can just sent it through a diffraction grating of known spacing, and measure the spacing between the bright spots. Or, if you want to be more precise, you can use a Michelson interferometer (which is what's in a lot of commercial wavemeters).
If you're worried about thermal emission over a broad range of infrared wavelengths, then you need a spectrometer of some sort. A grating monochromator world be the simplest thing, and probably work over the largest range of wavelengths. If you care about near-infrared (shorter than about 2 microns), there's this commercial unit, which I haven't used, but the other spectrometers we have from them are pretty good.
A: You are looking for a lambdameter. There are various ways to build one, but you can also buy one, e.g. http://www.photonicsonline.com/product.mvc/Lambdameter-LRL-005-0001 . 
They are often spectrometers, but, if you are analysing light with a narrow spectrum, an interferometric system gives you the best precision. The idea is to build an interferometer with a moving mirror, and counting the fringes during the movement gives you the wavelength if you know the amplitude of the movement. Of course, the best way to know the amplitude of the movement is to count the fringes of a known radiation (usually given by HeNe laser)
