When the source is removed farther , only intensity will decrease but frequency of incident light remain same .
due to which K.E remains same as KE=hf - hfo
Stopping potential is negative potential provided to
stop electron with max. KE and KE is constant
so stopping potential also remains constant.

Stating the photoelectric effect

The photoelectric effect refers to the phenomenon where light incident on a metal surface causes the ejection of electrons from the metal. This effect can be explained by the particle nature of light, where light is considered to be composed of photons, which are packets of energy.

Understanding the stopping potential

The stopping potential refers to the potential difference that must be applied across the metal surface in order to prevent the emitted electrons from reaching the other electrode. In other words, it is the minimum potential required to bring the photoelectric current to zero.

Analyzing the effect of distance on stopping potential

When the point source of light is moved farther from the emitting metal, the intensity of light incident on the metal decreases. This decrease in intensity implies a decrease in the number of photons incident on the metal surface per unit time.

Decrease in the number of incident photons

When the number of incident photons decreases, the number of electrons emitted from the metal surface also decreases. This is because each photon can only eject one electron. Therefore, with fewer photons, there will be fewer emitted electrons.

Effect on stopping potential

Since the stopping potential depends on the number of emitted electrons, a decrease in the number of emitted electrons will result in a decrease in the stopping potential. This means that a smaller potential difference will be required to prevent the reduced number of electrons from reaching the other electrode.

Conclusion

In conclusion, when the point source of light is moved farther from the emitting metal, the stopping potential remains constant. This is because the decrease in the intensity of light leads to a decrease in the number of emitted electrons, which in turn leads to a decrease in the stopping potential required to prevent the reduced number of electrons from reaching the other electrode. Therefore, the stopping potential remains constant in this scenario.