The minimum frequency for the photoelectric effect of a zinc plate is 9.7 × 1014 Hz. What will be the kinetic energy of an ejected electron when a photon with a wavelength 200 nm (2.00 × 10 7 m) strikes it?

Answer 1

200 nm = 2• 10 ^-8 m (! ! !)
Einstein's photoelectric equation:
ε =W + KE,
ε = h•c/λ = 6.63•10^-34•3•10^8/2•10^-7 =9.9•10^-19 J.
W =h•f= 6.63•10^-34•9.7•10^14 =6.43•10^-19 J.
KE = ε – W = 9.9•10^-19 - 6.43•10^-19 =3.47•10^-19 J.