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

Cathode rays are made up of, Cathode rays are made up of: (1) Positivel...

Cathode rays are made up of: (1) Positively charged particles (2) Negatively charged particles (3) Neutral particles (4) None of these Ans: (2)Negatively charged pa

Explain the working of a refrigerator, Explain the working of a refrigerato...

Explain the working of a refrigerator A refrigerator is the reverse of a heat engine. Here the working substance extracts heat Q2 from the cold reservoir at temperature T2, som

Magnetic effects of current, a)  Explain the magnetic effects of current? ...

a)  Explain the magnetic effects of current? b)  Do the diagram to show the direction of motion of the conductor:

What are plastics, Plastics are (A) Good conductors of heat. (B) ...

Plastics are (A) Good conductors of heat. (B) Good conductors of electricity. (C) Bad conductors of electricity. (D) High density. Ans: Plastics are Bad

Illustrate the electric field lines of a point charge q, The electric field...

The electric field E because of a point charge at any point near it is explained as where q is the test charge and F is the force acting on it. What is the physical significance of

Determine the corresponding set of electric field lines, Specified a set of...

Specified a set of equipotential surfaces how does one determine the corresponding set of electric field lines? Feedback: An equipotential surface signifies a set of poin

Project, i want to make a project of electromagnetic induction

i want to make a project of electromagnetic induction

Optics, Examples of pure and impure soectrum

Examples of pure and impure soectrum

Explain newtons first law, Explain Newtons First Law An object will rem...

Explain Newtons First Law An object will remain at rest or move with constant velocity until acted upon by a net external force. (A non-accelerating reference frame is known

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