Photoelectric effect is the emission of electrons from a metal surface when irradiated by light or electromagnetic waves as shown in Diagram below. (Ponor, CC BY-SA 4.0, via Wikimedia Commons)
Diagram below shows the apparatus used to study the characteristics of photoelectric effect. (Ponor, CC BY-SA 4.0, via Wikimedia Commons)
This effect provides evidence that light is quantised.
Photoelectrons are the electrons emitted from the metal surface due to photoelectric effect.
Photoelectrons are emitted with different kinetic energy.
The value of Planck’s constant can be determined from the photoelectric effect using a photocell in the circuit.
Light of a certain wavelength, \(\lambda\) is irradiated onto the cathode of the photocell.
Rheostat is adjusted so that the reading of milliammeter drops to zero.
Reading of voltmeter, \(V\) is recorded.
Lights of different wavelengths, \(\lambda\) are used, and the corresponding values of \(V\) are recorded.
A graph of \(V\) against \(\frac{1}{\lambda}\) is plotted as shown in Diagram below. Graph of \(V\) against \(\frac{1}{\lambda}\)
The value of Planck’s constant is determined from the gradient of the graph.