Question

Two operators, α and β, are said to commute when ____________

(a) α = β

(b) α + β = 0

(c) αβ = βα

(d) α^2 = β^2

I had been asked this question by my college professor while I was bunking the class.

The origin of the question is Linearity & Superposition in portion Quantum Physics of Engineering Physics I

Answer 1

Right answer is (c) αβ = βα

The explanation: Two operators, α and β, are said to commute when αβ = βα. If the same is not true, then the two operators are not commutable.