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

Work, Why the work called scalar quantity?

Why the work called scalar quantity?

Coupled harmonic oscillators, Coupled Harmonic Oscillators Two easy pen...

Coupled Harmonic Oscillators Two easy pendulums connected through a spring. The mass of one of the pendulums may be varied. Within mathematical rounding errors, the resolution

Show the biasing of a light emitting diode, With the help of a diagram, sho...

With the help of a diagram, show the biasing of a light emitting diode (LED). Give its two benefits over conventional incandescent lamps.

Ballistic missile, why ballistic missile is unpowered and unguided

why ballistic missile is unpowered and unguided

Different semiconductor materials: germanium, (1)          Melting point...

(1)          Melting point : 936 0 C (2)          Atomic number : 32 (3)          Energy gap : 0.6ev (4)          It is a gray metallic looking mat

Similarities in construction of MOSFET and JFET, Similarities in Constructi...

Similarities in Construction of MOSFET and JFET (i)  JFET is a three terminal semiconductor device (source, drain and gate) in which current conduction is by majority carriers

Explain how tunneling takes place in forward bias, Describe how tunneling t...

Describe how tunneling takes place    When  tunnel  diode  is  forward  biased,  its  initial  behaviour  is  similar  to  that when it's reverse biased. Now, some of the fille

In a plot of photoelectric current versus anode potential, In a plot of pho...

In a plot of photoelectric current versus anode potential, how does 1. The saturation current varies with anode potential for incident radiations of dissimilar frequencies but s

Light, what is light

what is light

Free-particle, Free-particle A.  Suppose that the wavefunction for a f...

Free-particle A.  Suppose that the wavefunction for a free-particle is given by the wavefunction Find the value of A that normalizes Ψ (x). B.  The Hamiltonian oper

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