The figure (1) shows the variation of photo current with anode potential for a photo-sensitive surface for three different radiations. Let ${\mathrm{I}}_{\mathrm{a}},{\mathrm{I}}_{\mathrm{b}}\text{ and }{\mathrm{I}}_{\mathrm{c}}$ be the  intensities and $f_a,f_b\text{ and }{f}_c$ be the frequencies for the curves a.b and c respectively
 

• A

  ${\mathrm{f}}_{\mathrm{a}}={\mathrm{f}}_{\mathrm{b}}\text{ and }{\mathrm{I}}_{\mathrm{a}}\ne {\mathrm{I}}_{\mathrm{b}}$

• B

  ${\mathrm{f}}_{\mathrm{a}}={\mathrm{f}}_{\mathrm{c}}\text{ and }{\mathrm{I}}_{\mathrm{a}}={\mathrm{I}}_{\mathrm{c}}$

• C

  ${\mathrm{f}}_{\mathrm{a}}={\mathrm{f}}_{\mathrm{b}}\text{ and }{\mathrm{I}}_{\mathrm{a}}={\mathrm{I}}_{\mathrm{b}}$

• D

  ${\mathrm{f}}_{\mathrm{b}}={\mathrm{f}}_{\mathrm{c}}\text{ and }{\mathrm{I}}_{\mathrm{b}}={\mathrm{I}}_{\mathrm{c}}$