Question

In the figure shown an observer O₁ floats (static) on water surface with ears in air while another observer O₂ is moving upwards with constant velocity v₁ = v/5 in water. 

The source moves down with constant velocity v_s = v/5 and emits sound of frequency f. 

The velocity of sound in air is v and that in water is 4v. For the situation shown in figure

(a) The wavelength of the sound received by O₁ is 4v/ 5f 

(b) The wavelength of the sound received by O₁ is v/ f 

(c) The frequency of the sound received by O₂ is 21f / 16 

(d) The wavelength of the sound received by O₂ is 16v/ 5f

Answer 1

Correct option: (a, b, c)

Explanation: 

For observer O₁,

For O₂, there is change of medium, hence at the surface of water, keeping frequency unchanged