Question

From metal of workfunction 2 eV, the photon of energy 1 eV will A) detach electron from surface B) not detach electron​

Answer 1

Answer:

Not even a single electron will be emitted

By definition  the work function is the minimum energy (in electron volts) needed to remove an electron from a solid to a point immediately outside the solid surface (or energy needed to move an electron from the Fermi level into vacuum).

Hence, the work function of metal is 4.5 eV this means that the energy necessary to emit electrons from metal surface is 4.5 eV. But the incident photons are of energy 2.5 eV, which is not sufficient to emit electrons from metal surface hence no electron will emit from the metal surface.