Lasers — CSIR Net PYQ (Question 2)

A Lasers previous-year question (PYQ) from Atomic and Molecular Physics (CSIR Net). Read the question, check the correct answer, then practise the full topic.

Question 2 of 14 · 3.5 marks

In a two-state system, the transition rate of a particle from state 1 to state 2 is

t_{12}

, and the transition rate from state 2 to state 1 is

t_{21}

. In the steady state, the probability of finding the particle in state 1 is

1 $\frac{t _{21}}{t _{12} + t _{21}}$
2 $\frac{t _{12}}{t _{12} + t _{21}}$
3 $\frac{t _{12} t _{21}}{t _{12} + t _{21}}$
4 $\frac{t _{12} - t _{21}}{t _{12} + t _{21}}$

Correct answer: Option 1

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This Lasers PYQ is part of the Atomic and Molecular Physics section of CSIR Net. Browse more Lasers questions or join the PhysicsByAaryan live batch for full conceptual coverage.