# Explain why (or how) in a sound wave, a displacement node is a pressure antinode and vice-versa?

#1

Explain why (or how)
(i) in a sound wave, a displacement node is a pressure antinode and vice-versa?
(ii) bats can ascertain distances, directions, nature and sizes of the obstacles without any eyes?
(iii) a violin note and sitar note may have the same frequency, yet we can distinguish between the two notes?
(iv) solids can support both longitudinal and transverse waves but only longitudinal waves can propagate in gases, and
(v) the shape of a pulse gets distorted during propagation in a dispersive medium?

#2

(i) Node It is a point where the amplitude of oscillation is zero, i.e. displacement is minimum. As pressure is inversely related with displacement, i.e. when displacement will be minimum pressure will be maximum.
Antinode At this point displacement is maximum, i.e. amplitude of oscillation will be maximum and hence pressure will be minimum as it is inversely related.
(ii) Bats emit ultrasonic waves of large frequencies. These waves will be reflected by the obstacles in their path. The reflected rays received by the bat will give idea about the obstacle, i.e. distance, direction, size and nature.
(iii) As relative strengths of notes are different in two notes of violin and sitar.
Although frequencies are same, we will distinguish by their strengths.
(iv) The reason behind is that solids have both the elasticity of
volume as well as shape. Whereas gases have only the volume elasticity.
(v) As in the dispersive medium wavelengths are different,hence the velocities, therefore the shape of the pulse gets distorted.