The electron emitted in the photoelectric effect is called a photoelectron.
Of current passes through the circuit in photoelectric effect then the current is called photoelectric current.
When all the photoelectrons emitted by the cathode reach the anode then the current flowing in the circuit at that instant is known as saturated current.
The minimum magnitude of the negative potential of the anode with respect to the cathode for which current is zero is called stopping potential.
The negative potential of the anode with respect to the cathode which is less than stopping potential is called retarding potential.
Observation made by Einstein
A graph between the intensity of light and photoelectric current is found to be a straight line. Photoelectric current is directly proportional to the intensity of incident radiation. In this experiment the frequency and retarding potential were constant.
A graph between photoelectric current and the potential difference between cathode and anode is found.
If the intensity is increased then the saturation current is increased by the same factor by which intensity increases. Stopping potential is the same, so the maximum value of kinetic energy will be the same.
If the light of different frequencies is used then as v increases, stopping potential increases which means the maximum value of kinetic energy increases.
The minimum frequency of electromagnetic radiation which can produce a photoelectric effect, which is called threshold frequency.
The maximum wavelength of radiation which can produce a photoelectric effect is called threshold wavelength.
It is also observed that the photoelectric effect is an instantaneous process. When light falls on the surface electrons start ejecting without taking any time.