[tommy2yk]

im just stating some revision for my first year exams and have come across something that i know is quite simple, and has been explained to me once already, but i didnt write it down...
for an s orbital the amplitude of the radial wavefunction is non 0, but all others (p, d etc) start at the origin, (in a 'radial wavefunction v. radius' graph) why is this?
also why does the radial distribution function start at the origin of all graphs which are also plotted against radius.
sorry for this pretty trivial question.