intensity of wave at that point

the answer is 0.304V........... Fe2+ + 2e– border=0Fe Eo = – 0.440V, just convert this as a backward reaction......... 0Fe=Fe2+ + 2e– (E.=0.440V)...TAKE THIS AS EQUATION 1 NOW U HAVE OTHER equation in the question........... Fe3+ + 3e– border=0Fe (E.= -0.036V).............TAKE THIS AS EQUATION2 now add 1,2 both lhs,rhs respectively now cancel the common elements using basic stoichiometry.....u get ur required equation....whose E=(E1+E2)=(0.44-0.036)=0.304.............. GOT IT?..........................

electric potential at a point due to a charge is given by the work done by that charge in moving a unit positive charge from infinity to that point.