P=Intensity×Area=6.4×10−5W−cm−2×1 cm2=6.4×10−5 W
For photoelectric effect to take place, energy should be greater than work function
Now,
E=1240310=4 eV>2 eV
Therefore, photoelectric effect takes place
Here n is the number of photons emitted.
n×E=I×A⟹n=IAE=6.4×10−56.4×10−19=1014
Where, n is number of incident photon
Since, 1 out of every 1000 photons are sucessfull in ejecting 1 photoelectron
Therefore, the number of photoelectrons emitted is
=1014103
∴x=11