Population inversion, Physics

Assignment Help:
population inversion
  • The process in which the number of electrons (N2) in a higher energy state called ‘metastable state of an active medium is increased to a value greater than the number of electrons (N1) in the ground state (i.e.N2 > N1) is called population inversion.
  • There are certain special substances or systems in which the electrons, once excited can remain in the higher energy state for longer times.
  • Such systems are called Active systems or Active Media.
  • Active systems are generally compounds or mixtures of different elements.
  • Consider three electronic states 1,2,3, in an active medium. (Refer text book for diagram.
  • Normally Large number of electrons exist in the Lowest energy state called ground state.
  • Let this number be N1 when photons of energy equal to the difference between E3 and E1 are incident, the electrons from state (1) are excited to state (3) because of absorption. But the property of the state (3) is such that the life time of electrons
  • in the state is very short, of the order 10-8 seconds. 
  • Of course most electrons return to state (1) from state (3) by spontaneous emission, but some electrons go to state (2) also.
  • Therefore, the electrons from the state (3) undergo a quick transition to the state (2) by emitting only a small energy (E3 - E2) which is simply absorbed as the thermal energy by the medium itself.

Related Discussions:- Population inversion

Vitreous enamel capacitors, These capacitors are made using vitreous enamel...

These capacitors are made using vitreous enamel on mixture of silica, alkali oxides and fluorides as dielectrics. These capacitors are formed by spraying vitreous lacquer on metal

Plane and convex mirrors, (a) You have studied that plane and convex mirror...

(a) You have studied that plane and convex mirrors produce virtual images of objects. Can they generate real image under some circumstances? Explain. (b) A virtual image we a

Illustrate how do fireworks turn into shapes like hearts, Q. Illustrate how...

Q. Illustrate how do fireworks turn into shapes like hearts as well as stars? Answer:- The fireworks creators have worked several decades to figure these things out. There

Motion, How do objects move in one dimension?

How do objects move in one dimension?

How many sizes are there of lighting fiber optic, How many sizes are there ...

How many sizes are there of lighting fiber optic? Literally hundreds, by some microns to over an inch into diameter, multicore and solid core, and square shaped ribbons, sheet

What are the applications of transistors? , A transistor is a semiconducto...

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least 3 terminals for co

Determine the pressure - hydraulics and hydrology, Points A and B are separ...

Points A and B are separated by 3000 ft of new 6-in schedule-40 steel pipe. 800 gpm of 60 deg F of water flow from point A to point B. Point B is 60 ft above point A. What must be

LOGIC, : Construct a regular proof to derive the conclusion of the followin...

: Construct a regular proof to derive the conclusion of the following argument: 1. (A & U) ~R 2. ~(~R v ~A) / ~U

Explain about cut-off or stopping potential, Q. What is cut-off or stopping...

Q. What is cut-off or stopping potential? The minimum negative (retarding) potential specified to the anode for which the photo electric current becomes zero is called the cut

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd