Given,
Work function, Wo=3.5eV
Potential, V=Ek=1.2eV
According to Einstein’s photoelectric equation,
hν=Wo+12mv2
hν=3.5+1.2
hν=4.7eV
The light rays having photons of energy 1.8 eV are falling on a metal surface having a work function 1.2 eV. What is the stopping potential to be applied to stop the emitting electrons