Sodium and copper have work functions $2.3\text{ev}$  and $4.5\text{ev}$  respectively, then the ratio of the threshold wavelengths is nearest to

Work function ${\text{w}}_{\text{1}}=2.3\text{ev}$

Work function ${\text{w}}_{\text{2}}=4.5\text{ev}$

Ratio of threshold wavelengths $\frac{{\text{λ}}_{{\text{0}}_{\text{1}}}}{{\text{λ}}_{{\text{0}}_{\text{2}}}}=?$

Threshold wavelength ${\text{λ}}_{\text{0}}\text{=}\frac{\text{hc}}{\text{w}}$

$\frac{{\text{λ}}_{\text{1}}}{{\text{λ}}_{\text{2}}}\text{=}\frac{{\text{w}}_{\text{2}}}{{\text{w}}_{\text{1}}}$

$=\frac{4.5}{2.3}\approx 2:1$