Question

What describes how the de Broglie wavelengths of two objects compare, assuming they are travelling at the same speed?
A. The wavelengths are the same.
B. The less massive one has a shorter wavelength.
C. The more massive one has a shorter wavelength.

Answer 1

λ = h / (mv)

h is plancks constant.
v is kept constant.

∴ λ ∝ 1/m

Hence, more massive one has a shorter wavelength.