Answer 1

By using Einstein's photoelectric equation is, K. E. = hv - Φ or hv = Φ + K. E. we can say that the emission of electrons takes place only if the incident energy is greater than the work function of the material.

In the given case, total incident energy =2 × 2.5 eV = 5 eV
The work function of aluminum, Φ = 4.2 eV

∵ Incident energy is greater than the work function of the material, hence the emission of electrons will take place.