Two identical, photocathodes recieve light of frequencies $f_1$ and $f_2$. If the velocities of the photoelectrons (of mass m) coming out are respecitvely $\nu_1$ and $\nu_2$, then :

Question

( A ) $\nu_1 - \nu_2 = [\frac{2h}{m} (f_1-f_2)]^{^{1/2}}$
( B ) $\nu_1^2 - \nu_2^2 = \frac{2h}{m} (f_1-f_2)$
( C ) $\nu_1 + \nu_2 = [\frac{2h}{m} (f_1+f_2)]^{^{1/2}}$
( D ) $\nu_1^2 + \nu_2^2 = \frac{2h}{m} (f_1+f_2)$