(i) A sound source emitting sound at a single frequency moves with constant speed along x-axis as shown in figure (a). A and B are two stationary observers. The three plots shown in figure (b) indicate the pressure function `P(x)` of the sound wave as recorded by the observer A, by B, and by another observer C who is at rest in the frame of the source. Which plot (marked as 1, 2 and 3) correspond to which observer?

(ii) Each of the two figures is rough illustration of the resulting waveform (y versus t ) due to overlapping of two waves. The four component waves have frequencies of 300 Hz, 200 Hz, 204 Hz and an unknown frequency `f=300+Deltaf`. Is `Deltaf` higher than or less than `4 Hz`?

Answer

(i) A-1 B-2 C-3
(ii) Less than 4 Hz