Define saturation current,stopping potential,and cut-off frequency in the context of the photoelectric effect.

(N/A) $1$. Saturation Current: In the photoelectric effect,as the accelerating potential (anode potential) is increased,the photoelectric current increases. Eventually,a stage is reached where all emitted photoelectrons reach the collector plate. At this point,the current becomes constant and does not increase further with an increase in potential. This maximum constant current is called the saturation current.
$2$. Stopping Potential: For a given frequency of incident radiation,the minimum negative (retarding) potential applied to the anode with respect to the cathode that stops even the most energetic photoelectrons is called the stopping potential or cut-off potential $(V_0)$. At this potential,the photoelectric current becomes zero.
$3$. Cut-off Frequency (Threshold Frequency): For a given photosensitive material,there exists a minimum frequency of incident radiation below which no photoelectric emission takes place,no matter how high the intensity of the radiation is. This minimum frequency is called the threshold frequency or cut-off frequency $(
u_0)$.