I have seen an equation about Hankle function,but I don't know why?
$(\frac{\partial^2 }{\partial r^2}+\frac{1}{r}\frac{\partial}{\partial r}+\beta )H^{(1)}_{0}(\sqrt{\beta} r)=\frac{4i\delta(r)}{2\pi r}$
what's more, is there a similar equation for the second kind modified bessel function. thanks.
http://math.stackexchange.com/questions/1607624/an-equation-about-hankle-function