- Phototube
A phototube is a type of gas-filled or
vacuum tube that is extremely sensitive to light in theultraviolet , visible, andnear-infrared ranges of theelectromagnetic spectrum .Operating principles
Phototubes operate according to the
photoelectric effect : Incomingphoton s strike aphotocathode , generatingelectron s, which are attracted to ananode . Thus current flow is dependent on the frequency and intensity of incoming photons. Unlikephotomultiplier tubes, no amplification takes place, so the current generated is typically on the order ofmicroampere s.Applications
One major application of the phototube was the reading of optical sound tracks for projected films. Phototubes were used in a variety of light-sensing applications until they were superseded by
photoresistor s andphotodiode s.External links
* [http://www.du.edu/~etuttle/electron/elect30.htm J.B. Calvert - Phototubes]
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