How does a photo detector detect?


by einstein2603
Tags: detect, photo
einstein2603
#1
Apr16-06, 05:30 AM
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Please guys I really need your help.

How does a photo detector detect? Can you also tell me where you got the info from.

thanks

einstein2603
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Hootenanny
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#2
Apr16-06, 05:41 AM
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Hello again einstein,

All 'photodetectors' operate using the photoelectric effect (or variants of). Basically, the photoelectric effect can be explained using quantum physics. Have you heard of the wave-particle duality of light? The photoelectric effect was the first source of firm evidence for the particle nature of light. Basically, light can be considered as a massless particle called the photon which has an energy of [itex]E = hf[/itex]. This site is very useful and should have all the information you need. If you have any questions, you can post them here

http://hyperphysics.phy-astr.gsu.edu...on.html#quacon

Regards,
~Hoot
andrevdh
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#3
Apr16-06, 12:28 PM
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Basically the photons causes the material that it falls on to become conductive - electrons (or their counterparts - holes) are generated (freed) from their bound states and become part of the sea of free charges that can flow in the material - that is the charge carriers are raised to a higher energy level by absorbing the energy from the photon. This increase in conductivity is sensed as an increase in current through the detector by a circuit connected to it. See for instance http://en.wikipedia.org/wiki/Photodiode


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