$\therefore \frac{1}{2} mv ^2=h v^2 h v_0=\frac{h c}{\lambda}-\frac{h c}{\lambda_0}$

$\therefore v^2=\frac{2 h c}{m}\left[\frac{1}{\lambda}-\frac{1}{\lambda_0}\right]$

$\therefore v ^2=\frac{2 hc }{ m }\left|\frac{\lambda_{-0}-\lambda_0}{\lambda_{00}}\right|^1$

$\left.\therefore v ^2=[ \frac{2 hc }{ m }\left\{\frac{\lambda_{-0}-\lambda^{\prime}}{\lambda_{-0}}\right\}\right]^{\frac{1}{2}}$