Formation and propagation of a pulse along a slinky
All along when we were discussing about transverse and longitudinal waves the disturbances, which cause them were continuous. But the disturbances always need not be continuous i.e., it might last only for a short duration.
For example: Take a slinky and fix one of its ends to a hook as shown in the fig (a). Keep the slinky horizontal and jerk its other end. You will see that a small hump has appeared in the straight slinky, which travels forward and looks as shown in fig (c) and fig (d). In this case, the slinky as a whole does not move forward, but its different parts move up and down about their mean positions. It is only hump or the disturbance, which moves forward along the slinky. Energy transfers from one part of the slinky to its other part. Such short disturbances are described as pulse.
Thus, a wave pulse can be defined as a sudden and short duration disturbance.
A periodic wave is a wave in which the particles of the medium oscillate continuously repeating their vibratory motion regularly at fixed intervals of time.