Physics · Dual Nature Of Radiation And Matter · NEET
Once the collector plate is positive enough, it pulls in every single electron that the metal emits per second. There are no extra electrons left uncollected. So raising the potential more cannot increase the current. That flat maximum is the saturation current. It is fixed by how many electrons are emitted per second, which depends on light intensity, not on the potential.
No. A small negative potential only turns back the slowest electrons, so the current drops but is still not zero. As you make the plate more negative, more electrons are turned back and the current keeps falling. Only at one exact value, the stopping potential V0, even the fastest electron is stopped, and the current finally becomes zero.
No, they are opposite ends of the graph. Saturation current is the maximum current on the positive-potential side (all electrons collected). Stopping potential is the negative voltage on the other side that makes the current zero. Saturation current tells you about the NUMBER of electrons (intensity). Stopping potential tells you about the maximum ENERGY of electrons (frequency).
Stopping potential depends only on the frequency (colour) of the light and the metal's work function, not on intensity. Brighter light of the same frequency gives more electrons, so the saturation current goes up, but the fastest electron has the same energy, so V0 stays the same. Increase the frequency and V0 increases (eV0 = h(nu) - work function).
It is small but not zero. Even with no accelerating voltage, some photoelectrons are emitted with enough kinetic energy to reach the collector on their own. So the current is positive at zero potential. You need an actual negative (retarding) potential to bring it down to zero.
A beam of light falls on a metal surface so that photoelectrons are generated. If the power of the light source decreases linearly with time t, then the variation of the photocurrent I and the magnitude of the stopping potential |V| with time is best represented by:
Photons of energy 5 eV are incident on a cathode C. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectrons will reach the anode A if the stopping potential of A relative to C is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Positive plate potential raises the current up to a fixed saturation value; negative (retarding) potential lowers the current until it reaches zero at the stopping potential V0.
The maximum, constant photoelectric current reached when the collector is positive enough to catch every electron emitted per second. It depends on light intensity, not on the potential.
The minimum negative potential on the collector that makes the photoelectric current exactly zero by stopping even the fastest electron. It is set by the light frequency and the metal's work function.
Some photoelectrons leave the metal with enough kinetic energy to reach the collector on their own, so a small current flows even with no accelerating voltage.
No. Higher intensity raises the saturation current (more electrons) but does not change the stopping potential, because the maximum electron energy depends on frequency, not intensity.
