Question

The source of sound generating of a frequency of 3 kHz reaches an observer with a speed of 0.5 times the velocity of sound in air. The frequency heard by the observer is?

(a) 1 kHz

(b) 3 kHz

(c) 4 kHz

(d) 6 kHz

I had been asked this question by my college professor while I was bunking the class.

My enquiry is from Stationary Waves topic in division Waves of Engineering Physics I

Answer 1

Correct answer is (d) 6 kHz

For explanation I would say: γ^‘=v/(v-vs)×γ

=v/(v-0.5γ)×3kHz=6kHz.