Photoelectric emission takes place

(i) Show that a free electron at rest cannot absorb a photon and thereby acquire kinetic energy equal to the energy of the photon. Would the conclusion change if the free electron was moving with a constant velocity ? (ii) If the absorption of a photon by a free electron is ruled out as proved in (i) above, how does photoelectric emission take place at all ?

Derive de Broglie wave equation for material particles. (b) Why does photoelectric emission not take place if the frequency of incident radiation is less than threshold frequency ?

Speed of photons in photoelectric emission is