Question

In $He-Ne$ laser, population inversion takes place between energy levels of neon atoms. Helium atoms have a meta - stable energy level.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

If both assertion and reason are true but reason is not the correct explanation of assertion

Answer 2

The transition in $He - Ne$ laser is shown below. An electric discharge in the gas pumps the helium atom to higher energy states (which is metastable state $\approx 10^{-8} s$ ). These He atoms collide with the ground state neon atoms and excite to higher states (levels) and produce in inverted population inversion causing a unidirectional photon beam (laser light).