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Name:  Harry W.
Status:  other
Age:  40s
Location: N/A
Country: N/A
Date: 2000-2001

How is it possible to measure the wavelength of light emitted from an Infra Red heating element?

The wavelength(s) of infrared radiation is measured with an instrument called an infrared spectrometer [or spectrophotometer]. It consists of a slit of variable width which forms an slit-image of the impinging infrared radiation. The infrared image is then focused by mirrors on to a grating [in older instruments this element could be a large crystal of NaCl] designed to diffract infrared radiation, that is spatially separate the radiation according to wavelength in much the same way a prism spatially separates the various wavelengths of visible light. The diffracted infrared radiation then passes through a second slit that shields the detector from all the diffracted radiation except a narrow bandwidth. This narrow bandwidth of radiation falls on an infrared detector. The infrared detector can be any number of devices that convert the radiation impinging upon it to an electrical signal that is amplified and displayed on some sort of chart. The detector can be a thermocouple, or any number of solid state devices.

I hope that is not more about "elephants" than you cared to know!

Vince Calder

Radios are sensors constructed to detect specific wavelengths much longer than infrared light. Televisions respond to specific wavelengths between radio and infrared. Digital cameras respond to wavelengths in the visible range. Just adjust the sensors so they notice slightly longer wavelengths and you have a camera with sensors that respond to infrared. By having the frequency/wavelength adjustment like a radio tuner, you can determine the wavelength by "tuning in" to the signal from the heating element.

Kenneth Mellendorf

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