Ans. LONGITUDINAL WAVES
Longitudinal waves are produced due to compressions and rarefactions. In these waves, particles of the medium move back and forth along the direction of propagation of the wave.
Longitudinal Nature of Sound Waves
The waves produced by a vibrating tuning fork are longitudinal waves. Before the vibration of tuning fork, density of air molecules on the right side is uniform (Fig.10.3-a) When the right prong of tuning fork moves form mean position O to B (Fig.11.3-b), it exerts some pressure on the adjacent layer of air molecules and produces a compression. This compressed air layer in turn compresses the layer next to it and so on. A moment later, the prong begins to move from B towards A (Fig.1!3-c). Now the pressure in the adjacent layer decreases and a rarefaction is produced. This rarefaction is transferred to the air layer next to it and so on. As the tuning fork moves back and forth rapidly, a series of compressions and rarefactions are created in the air. In this way, sound wave propagates through the air. As the direction of propagation of sound wave is along the direction of oscillating air molecules, therefore this shows the longitudinal nature of sound waves