Ripple factor in half wave rectification diode

[Princu]

Please Help.
I am not getting the concept of ripple factor in half wave rectification with the help of diode.The derivation done by our lecturer is not clear.Someone please explain the concept and its derivation.
Also it seems from the derivation given by our lecturer that there are two types of I(RMS).Also the current is broken down into some components.What is that?

 

[BvU]

You're not happy with what teacher lectured, but I have no idea where it is becoming unclear for you. Difficult to help. Wiki explains the concept and its derivation; anything in particular over there that's not clear ? If so, you can use the template to help helpers help you.