A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of 3 x 106 ms -1. The velocity of the particle is

Wavelength of a particle is given by λ=hpWhere  h  is  Planck's  constant.Wavelength  of  an  electron  is  given  by  λe=hpeBut  λ=λeSo,  p=peor   mv=meve   or    v=mevemPutting  the  under  given  datame=9.1×10−31kg,ve=3×106m/s,m=1 mg=1×10−6kgv=9.1×10−31×3×1061×10−6=2.7×10−18ms−1