JAMB - Physics (1994 - No. 38)
If light with photon energy 2eV is incident suitably on the surface of a metal with work function 3eV, then
no electron will be emitted
the few electrons emitted will have a maximum kinetic energy of 1eV
the few electrons emitted will have a maximum kinetic energy of 3eV
many electrons will be emitted
解释
An electron can only be emitted if photon energy is equal or greater than work function of the plate