Photoelectric effect and photocurrent drop

In summary, the conversation discusses the behavior of photocurrent when a potential is applied across it. The speaker found that the photocurrent did not drop to zero, but rather reached a steady value as the potential was increased. The anode voltage was increased negatively, but the speaker still obtained positive photocurrent, potentially due to not taking large enough negative values for the potential. The possibility of extrapolating to zero current is discussed, but it depends on the wavelength used and whether the data can be graphed as a straight line. The speaker used multiple wavelengths and the photocurrent was expected to drop like a 1/x graph. However, the expected behavior did not occur, and the other person in the conversation is unsure of what is causing this.
  • #1
hayyan1
9
0

Homework Statement



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 don't understand why this happend?
 
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  • #2
Was the anode at + or - relative to the cathode?
 
  • #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.
 
  • #4
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?
 
  • #5
I used yellow, turquoise, green, blue, violet. it isn't 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
 
  • #6
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.
 

1. What is the photoelectric effect?

The photoelectric effect is the phenomenon where certain materials, when exposed to light, emit electrons. This was first discovered by Heinrich Hertz in 1887 and explained by Albert Einstein in 1905.

2. How does the photoelectric effect work?

When a photon of light hits a material, it transfers its energy to an electron within the material. If the energy of the photon is high enough, the electron can break free from the material and become a free electron, creating a current.

3. What is the threshold frequency in the photoelectric effect?

The threshold frequency is the minimum frequency of light required to eject an electron from a material. If the frequency of the light is below the threshold frequency, no electrons will be emitted.

4. Why does the photocurrent drop over time?

The photocurrent drops over time because the material becomes saturated with free electrons. Once all available electrons have been emitted, no more current can be produced.

5. How is the photoelectric effect used in technology?

The photoelectric effect is used in various technologies such as solar panels, photodiodes, and photomultiplier tubes. These devices use the emission of electrons to convert light energy into electrical energy.

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