Question

Assuming that the smallest measurable wavelength in an experiment is 0.730 fm (femtometers), what is the maximum mass of an object traveling at 927 m·s–1 for which the de Broglie wavelength is observable?

Answer 1

1 fm = 1.0 × 10-15 meters 
so
0.610  fm x (1.0x10^-15 m / 1 fm)
                   = 6.1x10^-16 m
so the formula is
λ = h / mu 
so,
as we know mass value so by putting
m = (6.626*10^-34)/(6.1*10^-16*199)
    =(6.626*10^-34)/(1213.96*10^-16)
    = 5.45 x 10^ -21 
hope thats an answer for you