Question

When a piece of metal is irradiated with UV radiation (wavelength = 162 nm), electrons are ejected with a kinetic energy of 3.54x10^-19 J. What is the work function of the metal? (KE=hv-phi)

Answer 1

the energy of the incoming photons is:

E = hc/L

h=plancks constant = 6.62 x 10^-34 Js
c=speed of light 3.0 x 10^8 m/s
L=wavelength=1.62 x 10^-7 m

therefore, Total Energy E=(6.62 x 10^-34 Js) *(3.0 x 10^8 m/s)/(1.62 x 10^-7 m) = 1.23 x 10^-18J

KE of particles = Total energy given to the metal - work function

work function = Total energy given to the metal - KE of particles

               = 1.23 x 10^-18J - 3.54 x 10^-19 J
               = 8.74 x 10^-19 J