According to Einstein's photoelectric equation, E=W0+Kmax .......(i) where, W0= work - function, Kmax= mximum kinetic energy of emitted electron and E = energy of incident photon. If v is the frequency of incident radiations, then E=hv hv=W0+Kmax [From eq. (i)] ⇒ Kmax=hv−w0 According to problem