Question

Explain why or how : 

(a) in a sound wave, a displacement node is a pressure antinode and vice versa 

(b) bats can ascertain distance, 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

(a) At displacement node, the variation of pressure is maximum. Hence the displacement node is the pressure antinode and vice-versa. 

(b) Bats can produced and detect ultrasonic waves. Bats notice the time of reflected waves and they then estimate the distance of the object from them. From the intensity of reflected waves, they can estimate the nature and size of the object. 

(c) These instruments produce different overtones. Hence quality produced by them will be different.

(d) Solids possess both bulk modulus and shear modulus. So both longitudinal and transverse waves propagate through them. 

(e) When a pulse passes through a dispersive medium, the wavelength of wave changes, and so the shape of the pulse changes.