Problem 4.179

A stationary source sends forth monochromatic sound. A wall approaches it with velocity $u=33 \mathrm{~cm} / \mathrm{s}$. The propagation velocity of sound in the medium is $v=330 \mathrm{~m} / \mathrm{s}$. In what way and how much, in per cent, does the wavelength of sound change on reflection from the wall?