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

Step-by-step solution

Helium-neon laser uses a gaseous mixture of helium and neon. An electric discharge in the gas pumps the helium atoms to higher energy level, (which is meta stable energy level). Sequence of transitions in He-Ne laser. Then these helium atom excite the neon atoms to higher level by collision and produce an inverted population of neon atom which emit radiation when they are stimulated to fall to lower level.