In, case I given, incident wavelength, λ1=670.5nm Stopping potential, V1=0.48V In case II Incident wavelength, λ2=474.6nm Stopping potential is V2 . By using Einstein photoelectric equation, eV1=‌
hc
λ1
−φ0 where, h is Planck's constant =6.63×10−34Js c is speed of light =3×108ms−1 φ0 is work function ∴‌‌eV1=‌
hc
λ1
−φ0 ‌ and similarly, ‌eV2=‌
hc
λ2
−φ0 ⇒‌‌φ0=‌
hc
λ2
−eV2 From Eqs. (i) and (ii), we get ∴‌‌‌