Assuming that the smallest measurable wavelength in an experiment is 0.650 fm (femtometers), what is the maximum mass of an object traveling at 129 m·s–1 for which the de broglie wavelength is observable?

Hey there!:

Wavelength λ = 0.650 fm = 0.650* 10⁻¹⁵ m (1 fm = 10⁻¹⁵ m)

Speed v = 129 m/s⁻¹

Planck constant h = 6.626 * 10⁻³⁴ J.s

De Broglie equation: λ = h/mv

Mass m = h/λv

= 6.626 * 10⁻³⁴/ ( 0.650* 10⁻¹⁵ * 129)

= 6.626*10⁻³⁴ / 8.385*10⁻¹⁴

= 7.902*10⁻²¹ Kg

Hope that helps!