Photoelectric emission is observed from a surface for frequencies \[{{v}_{1}}\] and \[{{v}_{2}}\] of the incident radiation\[({{v}_{1}}-{{v}_{2}})\]. If the maximum kinetic energies of the photoelectrons in the two cases are in the ratio 1: k then the threshold frequency \[{{v}_{1}}\]is given by

• A. \[\frac{{{v}_{2}}-{{v}_{1}}}{k-1}\]
• B. \[\frac{k{{v}_{1}}-{{v}_{2}}}{k-1}\]
• C. \[\frac{k{{v}_{2}}-{{v}_{1}}}{k-1}\]
• D. \[\frac{{{v}_{2}}-{{v}_{1}}}{k}\]