- #1
cryptist
- 121
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Might be simple but I couldn't see. We can easily derive momentum operator for position space by differentiating the plane wave solution. Analogously I want to derive the position operator for momentum space, however I am getting additional minus sign.
By replacing $$k=\frac{p}{\hbar}$$ and $$w=\frac{E}{\hbar}$$ into the plane wave solution, we get
$$\Psi=e^{ipx/\hbar-iEt/\hbar}$$
Then taking the derivative with respect to momentum,
$$\frac{\partial\Psi}{\partial p}=\frac{ix}{\hbar}\Psi$$
Then I get,
$$\hat{x}=-i\hbar \frac{\partial}{\partial p}$$
It has additional minus sign. Where is my mistake and/or how do I derive the position operator for momentum space in the simplest way?
By replacing $$k=\frac{p}{\hbar}$$ and $$w=\frac{E}{\hbar}$$ into the plane wave solution, we get
$$\Psi=e^{ipx/\hbar-iEt/\hbar}$$
Then taking the derivative with respect to momentum,
$$\frac{\partial\Psi}{\partial p}=\frac{ix}{\hbar}\Psi$$
Then I get,
$$\hat{x}=-i\hbar \frac{\partial}{\partial p}$$
It has additional minus sign. Where is my mistake and/or how do I derive the position operator for momentum space in the simplest way?