Here, Incident wavelength, λ=200‌nm Work function, φ0=5.01‌eV According to Einstein's photoelectric equation eVs=hv−φ0 eVs=‌
hc
λ
−φ0 where Vs is the stopping potential eVs=‌
(1240‌eV‌nm)
(200‌nm)
−5.01‌eV =6.2‌eV−5.01‌eV=1.2‌eV Stopping potential, Vs=1.2V The potential difference that must be applied to stop photoelectrons =−Vs=−1.2V