When Schrodinger wave equation in polar coordinates is solved the solution for $\mathrm{\psi }$ is of the form $\mathrm{\psi }(\mathrm{r},\mathrm{\theta },\mathrm{\varphi })=\mathrm{R}\left(\mathrm{r}\right).\mathrm{Y}(\mathrm{\theta },\mathrm{\varphi })$ . Here R(r) is radial part of wave function and $\mathrm{Y}(\mathrm{\theta },\mathrm{\varphi })$ is angular part of the wave function. The region or space where probability of finding electron is zero is called nodal surface. If the probability of finding electron is zero then ${\mathrm{\psi }}^2(\mathrm{\rho },\mathrm{\theta },\mathrm{\varphi })=0\Rightarrow \mathrm{\psi }(\mathrm{\rho },\mathrm{\theta },\mathrm{\varphi })=0$  

If the radial wave function is equal to zero we get radial node and if angular part is equal to zero we get angular nodes. Total no. of nodes for any orbital = n – 1. Where ‘n’ is principal quantum number.