Question

f light of waveliength 330 nm is incident on each of the metals given below, which of these will

not emit photo electrons and why ?

Metal Work Function (eV)

Na 1.92

K 2.15

Ca 3.20

Mo 4.17​

Answer 1

Answer:

Mo 4.17

Explanation:

Wavelength of incident light  λ = 330 nm

So, energy of the incident light  E= hc/λ = 1240/ λ(in nm) eV

                                                       = 1240/330 = 3.7 eV

since, Work function of Mo = 4.17eV > 3.7 eV. Hence, No  photon emission.

Answer 2

Given:

Wavelength of light= 330 nm

To find:

Which of the given metals will not emit photo electrons.

Solution:

Work function of a metal = hc/λ = 1240/ λ

Therefore work function for 330 nm will be = 1240/330 = 3.76 eV

All the metals except Mo have a work function less than 3.7 eV, so all the metals will emit photo electrons when the light of wavelength 330 nm falls on them because they have a lower work function.

Therefore, Mo will not emit photo electrons because it has a higher work function.