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If we increase the distance between the collector plate and the emitter plate in the setup of the photoelectric experiment, then will there be any change in the stopping potential? (this thought comes into my mind as electric potential is defined as $V=E\cdot d$)

Also by making such a change, is the kinetic energy of the electron affected due to more time and distance given for collisions with other electrons which can cause its kinetic energy to be released consequently changing stopping potential?

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I like to think of potential as the depth of a well. When calculating the energy required to get a ball out of the well, it doesn't matter what the shape of the walls are and how long the slope is. It only matters how deep the well is relative to the surrounding ground.

So no, the distance won't matter at least in theory. I'm sure that if you move the plates to a ridiculous distance from each other other things will start interfering with the experimental results.

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No. There will be no change in stopping potential. Stopping potential is the potential required to stop the electron having the maximum kinetic energy. Here the maximum kinetic energy photon which undergoes no collision and retains the remainder of the photons energy. Increasing the distance will reduce the photoelectric current but will have no effect on the stopping potential.

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  • $\begingroup$ What about the kinetic energy of the electrons being lowered even further than before due to increasing the distance as now the electron will collide with more electrons and hence dissipate kinetic energy? $\endgroup$ – Schwarz Kugelblitz Jul 9 at 20:09
  • $\begingroup$ This will reduce the average kinetic energy of the electron but will not affect the maximum kinetic energy. $\endgroup$ – Nitin Shaji Jul 9 at 20:14
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Note that in the ideal case if we fix the potential between the plates then the electric field, the gradient of the potential, is $E = V/d$ and the work done is $W = F\cdot d = q\cdot E \cdot d$ so the two $d$s cancel and the total work done is the same (moving the plates apart means the electron has to go farther in the force field, but the force is also weaker).

The stopping potential is the energy required to stop the electron in the ideal case, excluding any external interactions like scattering.

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