Question

Shouldn't intensity increase the stopping voltage in the photoelectric effect?

Answer 1

Intensity of light is related to the number of photons. When intensity of the light increases, the number of photons increases and it increases the total energy of the light.

But it doesn't not increase the energy of a single photon. So the maximum kinetic energy an emitted electron does not increase by increasing intensity.

In photoelectric effect, the stopping potential is defined as the voltage necessary to stop the electron with the most kinetic energy from reaching the other side.

Since maximum kinetic energy of the emitted electron is not changing, the stopping potential will not change.

Answer 2

More intensity means more number of electrons so more probability of there being energetic electrons reaching the collecting plate so the stopping potential.