# If $\;\lambda_{0}\;$ and $\;\lambda\;$ be the threshold wavelength and wavelength of incident light , the velocity of photo electron ejected from the metal surface is :

$(a)\;\sqrt{\large\frac{2h}{m} (\lambda_{0} - \lambda)}\qquad(b)\;\sqrt{\large\frac{2hc}{m} (\lambda_{0} - \lambda)}\qquad(c)\;\sqrt{\large\frac{2hc}{m} ( \large\frac{\lambda_{0} - \lambda}{\lambda \lambda_{0}})}\qquad(d)\;\sqrt{\large\frac{2h}{m}(\large\frac{1}{\lambda_{0}}-\large\frac{1}{\lambda}) }$

[h (lamda. Lamda○)/2mc (lamda○-lamda)]>1/2