Which of following atomic energy system cannot be used in la

Which of following atomic energy system cannot be used in laser (unable to realize population inversion)? A 2-level energy system. A 3-level energy system. A 4-level energy system. An energy system with more than 4 levels. Answer:

Solution

the correct option is (A)

A 2-level energy system cannot be used in laser (unable to realize population inversion).

Since population inversion is not possible in a two level system.