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. `(Kv_(2)-v_(1))/(K-1)`
C. `(Kv_(2)-v_(1))/K`
D. `(Kv_(1)-v_(2))/(K-1)`