Physics > Basic Modern Physics > 5.0 Photoelectric Effect
Basic Modern Physics
1.0 Photon theory of light
2.0 Characteristics of photon
3.0 Wave Particle Duality
4.0 Emission of electrons
5.0 Photoelectric Effect
5.1 Laws of Photoelectric emission
5.2 Photoelectric equation
5.3 Photoelectric Current
5.4 Stopping potential
5.5 Graph between $K{E_{max}}$ and frequency
6.0 Radiation Pressure And Force
7.0 Photon Density
8.0 Force exerted by a light beam on a surface
9.0 Early Atomic Structures
10.0 Bohr Model of The Hydrogen Atom
10.1 Radius of Orbit
10.2 Velocity of electron in the $n^th$ orbit
10.3 Orbital frequency of electron
11.0 Energy of electron in the $n^{th}$ orbit
12.0 Basic Definitions
13.0 Atomic Excitation
5.3 Photoelectric Current
5.2 Photoelectric equation
5.3 Photoelectric Current
5.4 Stopping potential
5.5 Graph between $K{E_{max}}$ and frequency
10.2 Velocity of electron in the $n^th$ orbit
10.3 Orbital frequency of electron
$Fig. 2$ depicts a setup to study the variation of photo current $i$ with frequency of the incident light $f$ on the 
metal surface $A$.
- When $v$ is positive: Photoelectrons emitted from the plate $A$ are attracted by the positive plate $Q$. As $v$ is increased more and more electrons reach plate $Q$ and hence photo current increases to a certain value and then becomes constant (as the number of electrons emitted is constant which is equal to the number of photons in the incident light). This current is known as saturation current.
- When $v$ is negative: Photoelectrons emitted from the plate $A$ are repelled by the negative plate $Q$.As $v$ is decreased less and less electrons reach plate $Q$ and hence photo current decreases to a zero as $v$ equals to the stopping potential of the metal.
- When $v$ is zero: Photoelectrons emitted from the plate $A$ travel towards plate $Q$ but not all reach plate $Q$.
