The diagram above illustrates a structure of a typical photocell.

(i)  Identify each of the parts labelled A and B.
(ii) State one function each of A and B
(iii) Einstein’s photoelectric equation can be written as E = hf – Wo.  State what each of the terms E, hf and Wo represent.           
(b) A photon is incident on a metal whose work function is 1.32 eV.  An electron is emitted from the surface with a maximum kinetic energy of 1.97 eV. Calculate the frequency of the photon. [1 eV = 1.6 x 10-19 J]                                                 
(c)(i) Define half-life of a radioactive element.
(ii) Sketch a graph of the relation N = Noe-λt and indicate the half-life.