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

Object located between the center of curvature and focal, Object Located Be...

Object Located Between the Center of Curvature and the Focal Point Ray diagrams are meaningful tools for denoting the location of an image as generates through a concave mirror

High frequency alternating current by a loud speaker, Give reason that ultr...

Give reason that ultrasonics not be produced by passing high frequency alternating current by a loud speaker At these high frequencies, inductive reactance is so high where is

nuclear radiation detectors and dielectrics, What do you mean by dead time...

What do you mean by dead time in GM counter? Draw a neat diagram at GM counter and explain its working. Mention some of its applications. Give basic principle of Geiger-Muller coun

What are the affect does electricity have on the soil, Q. What are the affe...

Q. What are the affect does electricity have on the soil? Answer:- Electrical current and ions are able to cause certain molecules (and moisture) to adhere to soil. Large

Ammeters, Ammeters : Ammeters are used to measure current flow, as such...

Ammeters : Ammeters are used to measure current flow, as such they need to be inserted in series with the circuit under test so that the current to be measured flows through th

Maxwells electromagnetic equations, Starting from Maxwell's electromagnetic...

Starting from Maxwell's electromagnetic equations in vacuum, get the wave equations for the four fields vectors E, D, B and H.

Explain the molecular theory of surface tension, (i)  On the average, parti...

(i)  On the average, particles are separated by a distance of the order of 10-10 m and exert a force of attraction of the order of 10-11 N on each other. (ii)  The force of atta

Determine the self inductance of the primary coil, In the device shown in F...

In the device shown in Figure, when the current in the primary coil of 1000 turns increases linearly from 1A to 6A in 200ms, an e.m.f. of 15V is induced into the secondary coil of

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