a beam of helium atoms moves with a velocity of 20000 m/s. Find the wavelength of particles constituting with the beam

Dear Student,

Please find below the solution to the asked query:

According to de-Broglie relation: λ=hP=hmv

As 1 mol or 4 g of He contains 6.022 x 1023 atoms, then mass of single He atom = (4 / 6.022 x 1023 ) = 6.64 x 10-24 g

Hence, the wavelength = λ=hmv=6.626×10-34 Kg m2s-16.64×10-27 Kg×20000 ms-1=4.99×10-12 mλ = 499 pm

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