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

Circular motion, what happens to a conical pendulum when the bob splits int...

what happens to a conical pendulum when the bob splits into two parts such that one part remains attached to the string?

How fast is the submarine travelling - sound waves, A submarine is travelli...

A submarine is travelling toward a stationary detector. If the submarine emits a 260-Hz sound that is received by the detector as a 262-Hz sound, how fast is the submarine trav

Turning effect of forces, information about parallel forces and its types a...

information about parallel forces and its types and examples

In what direction does the particle move, If a negative charged particle en...

If a negative charged particle enters a magnetic field perpendicularly,then it follows a circular path.In what directn does the particle move---in clockwise or anticlockwise? So

Microwaves and radio waves, Microwaves and Radio waves: Microwaves are...

Microwaves and Radio waves: Microwaves are produced by high frequency electromagnetic oscillators in electric circuits. Microwaves are electromagnetic waves with wavelengths i

Determine the wavelength of the wave, A longitudinal wave with a frequency ...

A longitudinal wave with a frequency of 34 Hz takes 1.0 s to travel the length of a 2.5 m Slinky (see the figure). Determine the wavelength of the wave. λ = ( )m

Polarisation, production and analysis of diffrent polarised light

production and analysis of diffrent polarised light

Explain various types of equilibrium, Equilibrium can be spited in given ty...

Equilibrium can be spited in given types: (i) Stable equilibrium : After showing a charged particle from it's equilibrium point, if it goes back then it is called in stable equ

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