What are longitudinal waves? Explain with an example.

Longitudinal waves:
The waves in which particles of the medium vibrate along the direction of wave motion are called longitudnal motion.

As shown in Fig. below
Fig. Formation of longitudinal waves in a slinky.
i) Consider a slinky held horizontally and its one end tied to a rigid support.
ii) If we continuously give motion to its end slightly, the turns of the slinky begin to oscillate back and forth about their original positions along the length of the spring.
iii) These turns alternately come closer together and move away from the one another so that there are alternate regions of increased and decreased pressure. These regions are called ‘compressions’ and ‘rarefactions’ respectively.
iv) Thus, the waves in the slinky are longitudinal as the vibrations of the particles are along the direction of wave motion.