Photoelectric emission is observed from a surface for frequencies `v_(1) "and" v_(2)` of the incident radiation `(v_(1) gt v_(2))` . If maximum kinetic energies of the photo electrons in the two cases are in the ratio `1:K` , then the threshold frequency is given by:
A. `(v_(2)-v_(1))/(k-1)`
B. `(k" "v_(1)-v_(2))/(k-1)`
C. `(k" "v_(2)-v_(1))/(k-1)`
D. `(v_(2)-v_(1))/(k)`