User Account

All Pages

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

Relativity, Length contraction

Length contraction

What is acceptor circuit, Q. What is acceptor circuit ? Give the uses of it...

Q. What is acceptor circuit ? Give the uses of it. Acceptor circuit The series resonant circuit is frequently called an acceptor circuit. By proffering minimum impedan

Turning effects of forces, example of parallel forces

example of parallel forces

Properties of semi-conductors, Their conductivity lies between conductor an...

Their conductivity lies between conductor and insulator. Their resistivity is usually high and temperature coefficient of resistance is always negative. These are materials which a

Get interference pattern in youngs double slit experiment, What are the con...

What are the conditions to get interference pattern having good contrast in young's double slit experiment

Effect on elasticity by different causes, (i) Effect of temperature: ...

(i) Effect of temperature: (a) In general elasticity reduces as the temperature increases. (b) Invar is an exception. There is no effect of temperature on elasticity of in

Action and reaction with a roller skate, Action and reaction with a roller ...

Action and reaction with a roller skate Place a roller skate on a smooth floor. Step on the roller skate with one foot and take a step forward with the other. Observe that the

Physical quantities and measurement, what is constant

what is constant

How noisy is an illuminator, How noisy is an illuminator? It is very no...

How noisy is an illuminator? It is very noisy, slightly so or completely silent, depending upon the power source and the construction. There heat dissipation is something which

Polygon of force, Polygon of force This topic just builds on the previo...

Polygon of force This topic just builds on the previous Triangle of Forces. Consider three forces A, B and C.  A and B can be added by drawing a triangle to give a re

Write Your Message!

Captcha
Order Assignment

Featured Services

Order Now

Popular Subjects

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!

Submit Assignment

Academics

Major Subjects

Majors

Get In Touch

whatsapp: +91-977-207-8620

Phone: +91-977-207-8620

Email: [email protected]

TERMS & POLICIES

HELP & SUPPORT

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