bolometer bōlŏm´ətər, bə– [key], instrument for detecting and measuring radiation , e.g., visible light , infrared radiation , and ultraviolet radiation , in amounts as small as one millionth of an erg . The bolometer was invented in 1880 by Samuel P. Langley. Basically it consists of a radiation-sensitive resistance element in one branch of a Wheatstone bridge; changes in radiation cause changes in the electrical resistance of the element. The radiation-sensitive element may be a platinum strip, a semiconductor film, or any other substance whose resistance is altered by slight changes in the amount of radiant energy falling on it.
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