Question

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 sizes of the 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, and
(E) The shape of a pulse gets distorted during propagation in a dispersive medium.

Answer 1

Hint: Sound is a mechanical wave that is produced from the to and fro vibration of the particles of the medium through which the sound wave propagates. If a sound wave is moving from left to right in air, then particles of air will be displaced in both the directions as the energy of the sound wave passes through it.

Complete step by step answer:
When we consider question a:
We know that a node N refers to a point where the vibration of amplitude is minimum and pressure is maximum. On the other hand, an antinode is a point where the opposite happens, that is maximum vibration of amplitude and minimum pressure.
Hence, a displacement node is a pressure antinode and vice versa.
When we consider question b:
Bats are capable of emitting ultrasonic sounds with large frequencies and when these waves reflect from the obstacles in the path, they get an idea regarding direction, distance and nature of the obstacle.
When we consider question c:
Sitars and violins produce different overtones with varied strength. Hence their sounds are easily distinguishable even when they have the same frequencies.
When we consider question d:
It occurs because solids have elasticity of volume and elasticity of shape. Meanwhile gases possess only the elasticity of volume.
When we consider question e:
A sound pulse is a combined form of waves with varied wavelength. As they travel with different velocities in the same platform, the shape gets distorted.

Note:
Sound waves can be described by five major characteristics and they are Wavelength, Amplitude, Time-Period, Frequency and Velocity or Speed. This is applicable to all the waves including transverse waves like water waves, longitudinal waves like sound waves and the electromagnetic waves like light waves and radio waves.