We have to find the uncertainty in the location of a particle, in terms of its de Broglie wavelength , so that the uncertainty in its velocity is equal to its velocity.

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Let the mass of the particle be m and its velocity be v. It is given that the uncertainty in the velocity is equal to the velocity. Therefore, the uncertainty in the momentum of the particle will be

From the Heisenberg’s uncertainty principle we expect that the uncertainty in the position of the particle will be of the order of

where we have used that the de Broglie wavelength