Physics - Sound Wave Question with Solution | TestHub

Given,$v_s=90\mathrm{ }\mathrm{km} {\mathrm{h}}^{-1}=\frac{90\times 5}{18} \mathrm{m} {\mathrm{s}}^{-1}=25 \mathrm{m} {\mathrm{s}}^{-1}$

${\nu }_s=150\mathrm{ }\mathrm{Hz},$speed of sound,$v=340\mathrm{ }\mathrm{m} {\mathrm{s}}^{-1}$

Here, the source is an observer of reflected sound and moving towards the reflector (the cliff)

Thus,$v_o=25\mathrm{ }\mathrm{m} {\mathrm{s}}^{-1}$

Since, Doppler's equation for sound,

$\nu =\frac{v+v_s}{v-v_o}{\nu }_s=\frac{340+25}{340-25}\times 150$

$=\frac{365}{315}\times 150=173.88\mathrm{ }\mathrm{Hz}$

$\therefore \nu =174\mathrm{ }\mathrm{Hz}$