The wavelength is $120\text{ cm}$ when the source is stationary. If the source is moving with relative…
The wavelength is $120\text{ cm}$ when the source is stationary. If the source is moving with relative velocity of $60\text{ ms}^{-1}$ towards the observer, then the wavelength of the sound wave reaching to the observer will be (velocity of sound $= 330\text{ ms}^{-1}$)
$98\text{ cm}$
$140\text{ cm}$
$120\text{ cm}$
$1440\text{ cm}$
Solution
Phase difference, $\Delta\phi = k \cdot \Delta x$
$\Rightarrow \Delta\phi = \frac{2\pi}{\lambda} \times \Delta x = \pi \times (3.5 - 3) = \frac{\pi}{2} \left(\because k = \frac{2\pi}{\lambda} = \pi\right)$