Light of wavelength $\mathrm{\lambda }$ falls on metal having work function $\frac{\mathrm{hc}}{{\mathrm{\lambda }}_0}$. Photoelectric effect will take place only when

For each metal, there is a characteristic minimum frequency, ν⁰ (also known as threshold frequency) below which photoelectric effect is not observed. At a frequency $v\ge v^0$ , the ejected electrons come out with certain kinetic energy photoelectric effect becomes possible.

$$\begin{gathered} \mathrm{v}\ge {\mathrm{v}}^0 \\ \mathrm{\lambda }\le {\mathrm{\lambda }}_0 \end{gathered}$$