The work function

For photoemission energy ‘E’ of incident radiation must be more than or equal to work function ‘ϕ₀’ of the metal.

E ϕ₀ (The Condition for photoelectric emission)

E = hv = hc/λ

Where h = plank’s constant = 6.63 × 10^-34 J. sec

ν = frequency of radiation

c = speed of light = 3 × 10⁸ m/s

λ = wavelength of radiation

E = 6.63 × 10^-34 × 3 × 10⁸ / 330 × 10^-9

= 6.018 × 10^-19 J = 6.018 × 10^-19/1.6 × 10^-19 eV

= 3.76 eV

ϕ₀ = 4.2 eV as per question.

E < ϕ_0, therefore photoemission will not take place.

No photoemission will take place as work function is more than the photon energy of the incident radiation.