According to Einstein's theory of photoelectric effect:
\(hv = h{v_0} + KE\)
\(hv = h{v_0} + \frac{1}{2}m{v^2}\)
\(2h(v - {v_0}) = m{v^2}\)
\(\frac{{2h(v - {v_0})}}{m} = {v^2}\)
\(v \propto {(v - {v_0})^{\frac{1}{2}}}\)
\(\lambda \propto \frac{h}{{m{{(v - {v_0})}^{\frac{1}{2}}}}}\)
\(\lambda \propto \frac{1}{{{{(v - {v_0})}^{\frac{1}{2}}}}}\)