• # question_answer A stationary hydrogen atom emits a photon corresponding to the first line of Lymen series. If R is the Rydberg's constant, what velocity does the atom acquire if its mass is M A) $\frac{3Rh}{4\,M}$              B)    $\frac{Rh}{4\,M}$   C)   $\frac{Rh}{2\,M}$                D)   $\frac{Rh}{\,M}$

From conservation of momentum $MV=\frac{h}{\lambda }=hR\left( 1-\frac{1}{4} \right)\,\therefore \,V=\frac{3}{4}\,\frac{hR}{M}$ Hence, the correction option is (a).