Question

Differentiate between spontaneous and stimulated emission.

Answer 1

Sr. No.	Spontaneous emission	Stimulated emission
1.	The transition of an electron from the excited state to the ground state happens as a result of the natural tendency of the electron without the action of any external agent. The radiation produced as a result of such transitions is called as spontaneous radiation.	Stimulated emission of radiation is the process whereby photons are used to generate other photons that have exact phase and wavelength as that of parent photon.
2.	This phenomenon is found in LEDs, Fluorescent tubes.	This is the key process of formation of laser beam.
3.	There is no population inversion of electrons in LEDs.	Population inversion is achieved by various ‘pumping’ techniques to get amplification giving the LASER its name “Light amplification by stimulated emission of radiation.”
4.	No external stimuli required.	Thus stimulated emission is caused by external stimuli.
5.