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

Thermometers, advantages and disadvantages of maximum and minimum thermomet...

advantages and disadvantages of maximum and minimum thermometers

Newtons laws elephant and feather - air resistance, Elephant and Feather - ...

Elephant and Feather - Air Resistance Assume that an elephant and a feather are dropped off a extremely tall building from the similar height at the similar time. We will suppo

What are the favorable conditions for formation of cat ions, There are seve...

There are several conditions for formation of cat ions ? Low Ionisational potential ? Lesser Charge ? More atomic size of atoms forms cations easily ? Ions having Inert

Explain the term dielectric constant, Explain the term 'dielectric constant...

Explain the term 'dielectric constant' of a medium in terms of capacitance of a capacitor. Draw a graph showing variation of resistivity of carbon with temperature

How many joules of heat are radiated in 10 seconds, The potential differenc...

The potential difference across a 4 ohm resistor is 20 volts.  Suppose that all of the energy dissipated by this resistor is in the form of heat, how many joules of heat are ra

Determine dispersive power, A crown glass prism has refractive indices 1.57...

A crown glass prism has refractive indices 1.575 and 1.585 for blue and red colours. Determine its dispersive power. What are the basic conditions for a pair of thin prisms to p

Polarisation., nicol prism and its application how to easily undestanding t...

nicol prism and its application how to easily undestanding to teach the student

Calculate the velocity of top of the 12m tall hill, A sled and its rider, w...

A sled and its rider, with a total mass of 95 kg, are perched on top of a 25-m-tall hill. A second hill is 12 m tall (see the diagram below). The rider is given an initial push

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