Does anyone know how to caculate the ripple voltage of a half wave rectifier?

 

You mean just the ripple voltage or the ripple factor ? With or without filtering ? The ripple voltage is the RMS value of the resulting AC voltage wave, the ripple factor is the same divided by the CC component. But in order to calculate the RMS voltage you must know whether you have filtering or not. Calculating the RMS value of any wave is "easy": just square the signal function, integrate it over an entire period and then extract the square root.

Cheers !