The fig. shows the variation of photon current with anode potential for a photo-sensitive surface for three different radiation. Let `I_(a), I_(b) and I_(c)` be the intensities and `f_(a), f_(b) and f_(c)` be the frequency for the curves a,b and c respectively.
A. `f_(a) =f_(b) and l_(a) ne l_(b)`
B. `f_(a)=f_(c) and l_(a)=l_(c)`
C. `f_(a)=f_(b) and l_(a)=l_(b)`
D. `f_(a)=f_(b) and l_(a)=l_(b)`
