When an atom of an element is irradiated with a monochromatic light, what will happen in the case that the frequency of the light does not match the frequency needed for any of the several possible electronic transitions? Will the photon just pass through the atom? Or will it collide with the nucleus and get deflected or reflected? The nucleus only occupies a tiny space as compared to the atomic volume and so will a whole collection of such atoms be transparent to the respective monochromatic light as most photons just pass through the empty space in the atom?
first of all, you need to understand the use of frequency of light in abstracting elctrons from the metallic surfaces.we have a fix threshold frequency for a metallic surface, for which the incident light should have the frequency equal or greater than the threshold frequency.if any incident light have the same frequency as threshold frequency,then electrons will come out the attractive forces of electrons but never escape from the metal surface(this term is call work function of metal).elcetrons required a frequency above the threshold fruency because to overcome the attractive forces and remaining frquency will use to escape from metallic surfaces by gaining kinetic energy.