Question

Describe one example of a property (and give one equation) of electromagnetic radiation that is particle like.

Answer 1

Electromagnetic radiation (ER) have both wave as well as particle character. Its particle property can be explained by the Photoelectric effect. In this phenomena, when an electromagnetic radiation strikes a surface of metal, in certain cases, it causes ejection of electrom from metal surface with some kinetic energy.

This phenomena can be explained by the particle character of ER. This phenomenon can only be explained if we assume ER as particle packets of energy. When these packets of enery strikes metal surface it collides with loosely bound electrons of metal atoms outer most orbital which is easily ionisable. The ER then transfers energy to the electrons, if the transfered energy is sufficiently high to release the electron from atom's nuclear force, the electron starts flowing out of the metal surface. Well, there are certain conditions, the ER should have energy i.e., frequency (as, energy is directly proportional to frequency) higher than certain value. A portion of energy is used to release the electron and rest is used as kinetic energy (KE) of electron.

E(KE) = hn-E⁰ ; h:Plank's contant, n: frequency of incident light, E⁰:minimum energy required to release electron called metal work function

1. If hn is less than E⁰ the electron will not flow

2. If hn is greater than E⁰ the electron will flow and the KE will be according to yhe above equation

3. With increasing the n the KE will increase proportionally.

4. If intensity is increased keeping n fixed, it will cause increase in number of electron not the KE.