Explain why (or how) `:` (a) In a sound wave, a displacement node is a pressure antinode and vice-versa,
(b) Bats can ascertain distances, directions, nature and size of obstacles without any eyes,
(c) a violin note and sitar note may have the same frequency, yet we can distinguish between the two notes, (d) Solids can support both longitudinal and transverse waves, but only longitudinal waves can propagate in gases,
(e) The shape of pulse gets distorted during propagation in a dispersive medium.

Explanation

(a) A node is a point where amplitude is zero and pressure is maximum. Antinode is a point where amplitude is maximum and pressure is minimum. Therefore, displacement node coincides with pressure antinode.
(b) Bats emit ultrasonic waves of high frequency. These waves get reflected back by obstacles in their path. These reflected waves give them the idea of distance, direction, size of obstacle.
(c) A violin note and a sitar note may have the same frequency but the number of overtones produced by them are different. Hence, we can distinguish between the two notes.
(d) Because solids have the elasticity of volumne as well as the elasticity of shape but the gases have only volume elasticity.
(e) A sound pulse is a combination of waves of different wavelengths. As different waves travel with different velocities in a dispersive medium. Hence, the shape of the wave gets distorted.