When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however light of 600nm wavelength is sufficient for creating photoemission. What is the ratio of the work functions of the two emitters ?

2 : 1

$W=hv_0=hc/λ_0$

$\frac{W_1}{W_2}=\frac{λ_{02}}{λ_{01}}=\frac{600}{300}=2:1$