Light of wavelength $488\: nm$ is produced by an argon laser which is used in the photoelectric effect. When light from this spectral line is incident on the emitter, the cut-off potential of photoelectrons is $0.38\: V$. The work function of the material from which the emitter is made is

Question

$\begin {array} {1 1} (a)\;2.54\: eV & \quad (b)\;2.16\: eV \\ (c)\;21.6\: eV & \quad (d)\;2.26\: eV \end {array}$