The population inversion in helium-neon laser is produced by ?

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

Q. A) Monochromatic light of wavelength $632.8\text{nm}$ is produced by a helium-neon laser. The power emitted is $9.42\text{mW}$ .Find the energy and momentum of each photon in the light beam.

B) Monochromatic light of wavelength $632.8\text{nm}$ is produced by a helium-neon laser. The power emitted is $9.42\text{mW}$. How many photons per second, on the average, arrive at a target irradiated by this beam? (Assume the beam to have uniform cross-section which is less than the target area).

C) Monochromatic light of wavelength $632.8\text{nm}$ is produced by a helium − neon laser. The power emitted is $9.42\text{mW}$. How fast does a hydrogen atom have to travel in order to have the same momentum as that of the photon?"

Q. Monochromatic light of wavelength $632.8$ nm is produced by a helium-neon laser. The power emitted is $9.42mW$.
How fast does a hydrogen atom have to travel in order to have the same momentum as that of the photon?

Q. Monochromatic light of wavelength 632.8 nm is produced by a helium-neon laser. The power emitted is 9.42 mW.
Find the energy and momentum of each photon in the light beam,

Q. Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9mW. The number of photons arriving per sec. on the average at a target irradiated by this beam is :-