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Light Dependent Resistors?

  1. Oct 7, 2008 #1
    How does a light dependent resistor (photoresistor) work in terms of photons and electrons?

  2. jcsd
  3. Oct 7, 2008 #2


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    In an intrinsic semiconductor material like silicon, the electrons are held onto the atom strongly enough that the material is normally an insulator.
    A photon with enough energy can excite an electron up into the conduction band where it is more free of the atom and can move through the material carrying a current.
    The more light, the more free electrosn, the more current and th elower the resistance.
  4. Oct 9, 2008 #3


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    mgb_phys has given a good description of the physics behind light dependent resistors. FYI, they are typically made from cadmium sulfide (CdS).
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