Ripple factor: The output of the rectifier is of pulsating d.c. type. The amount of a.c. content in the output can be mathematically expressed by a factor called the ripple factor (γ). The ripple factor expresses how much successful the circuit is, in obtaining pure d.c from a.c. input.
Less is the ripple factor, better is the performance of the circuit.
Ripple Factor γ = R.M.S value of a.c component of output ⁄ Average or d.c component of the output