Monday, 31 August 2020

experimental physics - Experimentally measure velocity/momentum of a particle in quantum mechanics


In the context of quantum mechanics one cannot measure the velocity of a particle by measuring its position at two quick instants of time and dividing by the time interval. That is, $$ v = \frac{x_2 - x_1}{t_2 - t_1} $$ does not hold as just after the first measurement the wavefunction of the particle "collapses".


So, experimentally how exactly do we measure the veolcity (or say momentum) of a particle?


One way that occurs to me is to measure the particle's de Broglie wavelength $\lambda$ and use $$p = \frac{h}{\lambda}$$ and $$v = \frac{p}{m}$$ to determine the particle's velocity. Is this the way it is done? Is there any other way?




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