When light of wavelength 300 nm falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, light of wavelength 600 nm is sufficient for liberating photoelectrons. The ratio of the work function of the two emitters is

Question

$\begin {array} {1 1} (a)\;1:2 & \quad (b)\;2:1 \\ (c)\;4:1 & \quad (d)\;1:4 \end {array}$