Effect Of Intensity In Photoelectric Effect

In the photoelectric effect, intensity measures the number of photons arriving per second, whereas frequency fixes the energy of each individual photon. Since one photon ejects at most one electron, raising the intensity increases the number of emitted photoelectrons and hence the saturation photocurrent in direct proportion. However, the maximum kinetic energy of each ejected electron is set by $K_{max}=h\nu -{\varphi }_0$, which depends only on frequency and work function, not on how many photons strike the surface. Therefore the stopping potential, which measures $K_{max}/e$, remains unchanged when intensity alone is varied. Doubling both quantities is incorrect because energy per electron is intensity-independent. Saying stopping potential doubles while current stays fixed reverses the actual physics. Saying nothing changes ignores the proportional rise in current. This behaviour was historically impossible to explain with the classical wave theory of light, which wrongly predicted that brighter light should give faster electrons, and it formed the key evidence for the photon model in the NCERT chapter. The conclusion is internally consistent: more photons mean more electrons, but each electron's energy is unaltered.