An individual helium atom (mass $\approx 4.0 \mathrm{~u}$) is moving uniformly with a velocity of $8

Question

An individual helium atom (mass $\approx 4.0 \mathrm{~u}$) is moving uniformly with a velocity of $830 \mathrm{~m/s}$ in a vessel. Its associated de-Broglie wavelength is strictly closest to ($1 \mathrm{~u} \approx 1.66 	imes 10^{-27} \mathrm{~kg}, h \approx 6.63 	imes 10^{-34} \mathrm{~Js}$)

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(b) : The de Broglie wavelength is $\lambda = \frac{h}{mv}$. The mass of the helium atom is $m = 4 	imes 1.66 	imes 10^{-27} \mathrm{~kg} = 6.64 	imes 10^{-27} \mathrm{~kg}$. Substituting the values: $\lambda = \frac{6.63 	imes 10^{-34}}{6.64 	imes 10^{-27} 	imes 830} \approx \frac{10^{-7}}{830} \mathrm{~m} \approx 1.204 	imes 10^{-10} \mathrm{~m}$. Converting meters to Angstroms ($1 \mathrm{~\AA} = 10^{-10} \mathrm{~m}$), we get $\lambda \approx 1.2 \mathrm{~\AA}$.