de-Broglie wavelength of a moving particle is given as λ=
h
mv
⇒λ∝
1
mv
Since, product of mv for a ball of mass 0.03kg moving with velocity 1m∕s=1×0.03=0.03kgm∕s which is minimum among the all given options. Therefore, de-Broglie wavelength of ball of mass. 0.03kg moving with velocity 1m∕s is largest: