Physics · Dual Nature Of Radiation And Matter · NEET
When the collector plate is made positive, it pulls the emitted photoelectrons toward it. As you raise this positive voltage, more and more of the emitted electrons are collected. Once the voltage is high enough that ALL emitted electrons reach the collector, there are no more electrons left to add. So the current stays flat no matter how much you raise the voltage. This flat maximum is the saturation current. NCERT states: the photocurrent does not increase further because all the photoelectrons emitted by the emitter reach the collector.
No. Above the saturation point, extra voltage does nothing to the current. Voltage only controls HOW MANY of the already-emitted electrons get collected, not HOW MANY are emitted. Once every emitted electron is being collected, higher voltage has no electrons left to grab. To raise saturation current you must emit more electrons per second, and that means raising the light intensity.
The intensity (brightness) of the incident light. Higher intensity means more photons hit the metal per second, so more photoelectrons are emitted per second, so the saturation current is larger. Saturation current is directly proportional to intensity (for light above threshold frequency). Frequency and collector voltage do NOT change the saturation value.
They live on opposite ends of the current-voltage graph. Saturation current is the flat MAXIMUM current on the positive-voltage side and depends on intensity. Stopping potential is the small NEGATIVE voltage that makes the current drop to ZERO and depends on frequency (energy of electrons), not intensity. One measures how MANY electrons; the other measures how FAST the fastest electron is.
Number of photoelectrons emitted per second depends on how many photons arrive per second, which is intensity. Frequency sets the ENERGY of each photon (and so the speed of each electron), not the COUNT of photons. So changing frequency changes stopping potential, but the saturation current stays the same as long as intensity is unchanged.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the maximum photoelectric current reached when every photoelectron emitted per second is collected, so raising the voltage adds no more current.
Only on the intensity of the incident light (for light above threshold frequency). It is directly proportional to intensity.
No. Frequency changes the stopping potential (electron energy), not the number of electrons, so it does not change the saturation current.
It doubles, because twice as many photons arrive per second and twice as many photoelectrons are emitted per second.
On the positive collector-voltage side, as the flat horizontal (plateau) part of the curve.
