Question

A certain metal has a photoelectric work function value of 318.0 KJ/mol e^-. The metal is irritated with light having a wavelength of 345.0 nm. What is the maximum possible velocity of electrons ejected from the surface

Answer 1

Work function for 1 electron,

Eo = work function per mol of electron / Avogadro’s number

= 318.0 / (6.022*10^23)

= 5.281*10^-22 KJ

= 5.281*10^-19 J

Now calculate energy of electron:

Given:

lambda = 345.0 nm = 3.450*10^-7 m

use:

E = h*c/lambda

=(6.626*10^-34 J.s)*(3.0*10^8 m/s)/(3.45*10^-7 m)

= 5.762*10^-19 J

Now use:

KE of electron = E - Eo

= 5.762*10^-19 J - 5.281*10^-19 J

= 4.81*10^-20 J

Now use:

use:

KE = 0.5*m*v^2

4.81*10^-20 = 0.5*9.11E-31*v^2

v = 3.250*10^5 m/s

Answer: 3.250*10^5 m/s