What is Photoelectric Effect ?
In 1887, Hertz noticed that electrons are emitted from a metal surface when electromagnetic radiation falls. In 1888, Hallwachs showed experimentally that electrons are emitted from the Zinc plate when ultraviolet rays fall on the plate.
This phenomenon of emission of electrons from a metallic surface, when illuminated by the light of appropriate wavelength or frequency, is called the photoelectric effect. The electrons radiated in this process are called photoelectrons, and the current produced in the circuit is called photoelectric current. This effect has been found useful in electronic devices specialized for detecting light and precisely timed emissions of electrons. When the frequency of the incident UV light was smaller than a specified minimum value, known as the threshold frequency, then no electrons were emitted at all. This minimum frequency was dependent on the nature of the material of the emitter plate.
Einstein’s Photoelectric Equation
Albert Einstein in 1905 proposed that radiation energy is built up of discrete units called quanta of energy radiation. Each quantum of radiation has energy h, where h is the Planck’s constant and is the frequency of light radiation. A quantum of energy is absorbed by the electron and if it exceeds the minimum energy needed for the electron (Work Function 0 ). Einstein’s Photoelectric Equation is given as:
KE = hv – hv0
where
- KE is the kinetic energy of the photoelectron,
- h is Planck’s constant,
- v is the frequency of the photon
- v0 is the threshold frequency of material.
Photoelectric Effect and Wave Theory of Light
When light shines on a metal, electrons can be ejected from the surface of the metal in a phenomenon known as the photoelectric effect. This process is also often referred to as photoemission, and the electrons that are ejected from the metal are called photoelectrons. The wave theory of light states that light travels in the form of waves.
In this article, we will learn about the photoelectric effect, the wave theory of light and will try to answer whether they are related to each other or not.
Contact Us