What is the de Broglie wavelength of
$(a)$ a bullet of mass $0.040 \; kg$ travelling at the speed of $1.0 \; km/s$
$(b)$ a ball of mass $0.060 \; kg$ moving at a speed of $1.0 \; m/s$,and
$(c)$ a dust particle of mass $1.0 \times 10^{-9} \; kg$ drifting with a speed of $2.2 \; m/s$?

(N/A) The de Broglie wavelength is given by $\lambda = \frac{h}{mv}$,where $h = 6.626 \times 10^{-34} \; J \cdot s$.
$(a)$ Given $m = 0.040 \; kg$,$v = 1.0 \; km/s = 1000 \; m/s$.
$\lambda = \frac{6.626 \times 10^{-34}}{0.040 \times 1000} = \frac{6.626 \times 10^{-34}}{40} \approx 1.66 \times 10^{-35} \; m$.
$(b)$ Given $m = 0.060 \; kg$,$v = 1.0 \; m/s$.
$\lambda = \frac{6.626 \times 10^{-34}}{0.060 \times 1.0} \approx 1.10 \times 10^{-32} \; m$.
$(c)$ Given $m = 1.0 \times 10^{-9} \; kg$,$v = 2.2 \; m/s$.
$\lambda = \frac{6.626 \times 10^{-34}}{1.0 \times 10^{-9} \times 2.2} \approx 3.01 \times 10^{-25} \; m$.