Question

The wavelength is 120 cm when the source is stationary. If the source is moving with velocity of $60m/sec$ towards the stationary observer, then the wavelength of the sound wave reaching to the observer will be (velocity of sound = $330m/s$)

• A. 98 cm
• B. 140 cm
• C. 120 cm
• D. 144 cm

Answer 1

The correct option is A

98 cm

$n^{\prime }=n\left(\frac{v}{v-v_1}\right)\Rightarrow {\lambda }^{\prime }=\lambda \left(\frac{v-v_s}{v}\right)\Rightarrow {\lambda }^{\prime }=120\left(\frac{330-60}{330}\right)=98cm$