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Question:

If the momentum of an electron is changed by P, then the de-Broglie wavelength associated with it changes by 0.5. The initial momentum of electron will be :

P200

400P

100P

200P

Solution:

Initial momentum, Pi = h/λ

or Pi - P = h/(λ + 0.5)

100λ or Pi - P = Pi/(100 * 0.5) = Pi/50

or Pi = 50P/49 ≈ 200P