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Shortcut for Calculating Expectation Value of Momentum Operator

Shortcut Method for Calculating Expectation Value of Momentum Operator | Quantum Mechanics

Let, $\psi(x)$ = $\hat{A}$ f(x)

 

1. If f(x) is real: Expectation value of momentum operator will be 0.

i.e. $<\hat{p}>$ = 0

2. If the system is bound: Then also,

$<\hat{p}>$ = 0

(Irrespective of the fact that f(x) is real or imaginary.)

 


Problem: If $\psi(x)$ = 2i Sin(x), then find out expectation value for the momentum operator.

Solution:

Where, 2$i$ = $\hat{A}$ and f(x) = Sin(x)

Here, f(x) = Sin(x) $\leftarrow$ Real Quantity

So, $<\hat{p}>$ = 0

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