Q. If the velocity of a particle is increased three times, the percentage decrease in its de Broglie wavelength will be
(a) 33.3%
(b) 66.6%
(c) 99.9%
(d) 22.2%
Ans: (b)
Sol: λ = h/mv , λ’ = h/m(3v)
λ /λ ‘ = 3
% decrease in wavelength =( λ -λ ‘)/λ ×100
= (1−λ’ /λ) ×100 = (1−1/3)×100 = 66.6%