Question bank/JEE Advanced/Chemistry

Consider a helium (He) atom that absorbs a photon of wavelength $330 \mathrm{~nm}$. What is the change in the velocity (in $\mathrm{cm} \mathrm{s}^{-1}$ ) of He atom after the photon absorption?

(Assume: Momentum is conserved when photon is absorbed.

Use: Planck constant $=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}$, Avogadro number $=6 \times 10^{23} \mathrm{~mol}^{-1}$, Molar mass of $\mathrm{He}=4 \mathrm{~g} \mathrm{~mol}^{-1}$ )

Source: JEEBench (IIT Delhi) / JEE Adv 2021 Paper 2