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Homework Help: Photoelectric effect and photocurrent drop

  1. Nov 23, 2008 #1
    1. The problem statement, all variables and given/known data

    Does the photocurrent drop to zero when a potential across it is equal to the kinetic energy of electrons?, because i found this not to be the case, the photocurrent reached a steady value that didnt decrease further, as i increased the potential across the anode and cathode. I dont understand why this happend?
     
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  3. Nov 24, 2008 #2

    Redbelly98

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    Was the anode at + or - relative to the cathode?
     
  4. Nov 24, 2008 #3
    anode voltage was increased negatively so electron should be repelled from anode in theory, but for some reason i still was obtaining postive photocurrent, maybe i should have taken much larger negative values for potential, so current would eventually become zero?, however do you think i can extrapolate (with a curve of best fit) to zero current, because my graphs are curving towards zero photocurrent.
     
  5. Nov 24, 2008 #4

    Redbelly98

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    It depends. What wavelength(s) was/were used to generate the photocurrent? How high a voltage did you get to?

    Extrapolating reasonably depends on whether graphing the data generates a straight line. Does it?
     
  6. Nov 24, 2008 #5
    I used yellow, turquoise, green, blue, violet. it isnt ment to generate a straight line, for each frequency, the photocurrent (yaxis) is kind of meant to drop like a 1/x graph when plotted against the potential across the xaxis
     
  7. Nov 24, 2008 #6

    Redbelly98

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    That's weird. I would expect current to be zero if you go high enough in voltage, but I haven't done the experiment.

    Not sure what's going on.
     
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