• # question_answer Light of wavelength 4000 $\overset{\text{o}}{\mathop{\text{A}}}\,$ is incident on a sodium surface for which the threshold wave length of photo  electrons is 5420 $\overset{\text{o}}{\mathop{\text{A}}}\,$. The work function of sodium is    A) 4.58 eV B) 2.29 eV C) 1.14 eV D) 0.57 eV

[b] ${{W}_{0}}=\frac{12375}{{{\lambda }_{0}}(\overset{\text{o}}{\mathop{\text{A}}}\,)}=\frac{12375}{5420}=2.29eV$