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

Vectors, The helicopter view in fig. p3.29

The helicopter view in fig. p3.29

Write down the equation of electromagnetism, One of the Maxwell's e-m equat...

One of the Maxwell's e-m equations involves the curl of the electric field. Write down the equation and mention the law of electromagnetism which is shown by the equation.

Explain different logic gates, There are mainly three parts of Logic gates ...

There are mainly three parts of Logic gates (1)          The 'OR' gate (i) It has two inputs (A and B) and only one output (Y) (ii) Boolean expression is Y = A + B (iii

If the ray is a principal ray where does it go from there, Portrayed is a r...

Portrayed is a ray from an object which heads toward and then into a lens. Suppose if the ray is a principal ray where does it go from there? Ans: This is the simple p

Generate a gaussian random signal vector, Generate and plot a sampled sine ...

Generate and plot a sampled sine wave with f s =8kHz, of 4 seconds duration, with frequency ω 0 = Π/10 and amplitude A = 1 . 2. The waveform equation is x ( n )   =   A s

Besides solid, Besides solid, liquid, and gas, what is the fourth form of m...

Besides solid, liquid, and gas, what is the fourth form of matter? Ans: The fourth form of matter is plasma.

Wave, application of huygen''principle

application of huygen''principle

Explain the principle and working of a light emitting diode, Define, with t...

Define, with the help of a schematic diagram, the principle and working of a Light Emitting Diode. What criterion is kept in mind whereas choosing the semiconductor material for su

Elasticity, what is elasticity

what is elasticity

Why x-rays are not used in microscopes, Q. Why X-rays are not used in micro...

Q. Why X-rays are not used in microscopes? 1) The wavelength of X-rays is slighter than that of the visible light. 2) X-rays can't be focussed as visible radiations are foc

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