Caesium metal of work function [tex]2.0 eV[/tex] is illuminated with radiations of wavelength [tex]5.0\times10^{-7}m[/tex]. Calculate the:

(i)threshold wavelength of the metal;

(ii)maxium energy of liberated elecrons.

[tex][h=6.6\times10^{-34} Js; IeV=1.6\times10^{-19} J; c=3.0\times10^8 ms^{-1}][/tex]

Since threshold frequency and threshold wavelenght are not the same, am confused of the formula to use.

What is the best formula to use? Should I use [tex]\omega=hfo[/tex] or should use

[tex]E=\frac{hc}{\lambda}[/tex]