what are the laws of photo electric effect ?

CBSE Class 12-science Answered

what are the laws of photo electric effect ?

Asked by pksunilnair | 04 Dec, 2017, 09:27: AM

Expert Answer

Photo electric effect is not a law like newton's law, ohm's law. It is a physical phenomenon

Photoelectric effect, phenomenon in which electrically charged particles (genrally electrons) are released from material surface, when it absorbs electromagnetic radiation. The effect is often defined as the ejection of electrons from a metal plate when light falls on it. The radiant energy may be infrared, visible, or ultraviolet light, X rays, or gamma rays;

Photoelectric effect can not be explained by classical physics which assumes light is electromagnetic wave. But as per modern physics light behaves dual nature like particle and wave, This particle behaviour makes it possible to explain the observed photo electric effiect. As per this particle behavour, incident light consists of photon that penetrates the material and transfer energy to electron. After gaining the enegy, electron is knocked out of metal and the kinetic energy of electron is reduced by an amount φ which is known as workfunction of that material. Workfunction of a particular material can be defined as the energy required for electron to escape the metal.

The photo electric equation :- E_k = hν - φ ,

where E_k is kinetic energy of electron, h is plancks constant, ν is frequency of light and φ is work function of the material.

Important observation form the photo electric effect is

(1) maximum kinetic energy of the released electron is proportional to the frequency of incident light

(2) light intensity only increases the number of electrons thar are ejected from the metal

Answered by | 04 Dec, 2017, 01:11: PM