Two identical photocathodes receive light of frequency `f_(1) andf_(2)` if the velocites of the photo electrons (of mass `m`) coming out are repectively `v_(1) and v_(2)` then
A. `v_(1)-v_(2)=[(2h)/(m)(f_(1)-f_(2))]^(1//2)`
B. `v_(1)^(2)-v_(2)^(2)=(2h)/(m)(f_(1)-f_(2))`
C. `v_(1)+v_(2)=[(2h)/(m)(f_(1)+f_(2))]^(1//2)`
D. `v_(1)^(2)+v_(2)^(2)=(2h)/(m)(f_(1)+f_(2))`
