The maximum velocity of an electron emitted by light of wavelength $\mathrm{\lambda }$. incident on the surface of a metal of work function Φ, is

• A

  ${\left[\frac{2\left(\mathrm{hc}\right)+\mathrm{\lambda \varphi }}{\mathrm{m\lambda }}\right]}^{1/2}$

• B

  $\frac{2\left(\mathrm{hc}-\mathrm{\lambda \varphi }\right)}{\mathrm{m}}$

• C

  ${\left[\frac{2\left(\mathrm{hc}-\mathrm{\lambda \varphi }\right)}{\mathrm{m\lambda }}\right]}^{1/2}$

• D

  ${\left[\frac{2\left(\mathrm{h\lambda }-\mathrm{\varphi }\right)}{\mathrm{m}}\right]}^{1/2}$