In an experiment tungsten cathode which has a threshold wavelength 2300 Å is irradiated by ultraviolet light of wavelength 1800 Å. The maximum energy of emitted photo-electron will be –

1.2 eV 1.5 eV 1.6 eV 1.8 eV

1.5 eV

$K_{max}=hc(\frac{1}{λ}-\frac{1}{λ_0})=\frac{6.62×10^{-34}×3×10^8}{1.6×10^{-19}}(\frac{10^{10}}{1800-\frac{10^{10}}{2300}})=1.5eV$