Q 11-14-077JEE MainJEE Main 2022 (27 Jun, Shift 1)Easy
An observer moves towards a stationary source of sound with a velocity one-fifth of the velocity of sound. The percentage change in the apparent frequency is
Answer: (D) $20\%$
For an observer moving towards a stationary source:
$$f' = f\,\frac{v + v_o}{v} = f\left(1 + \frac15\right) = 1.2f$$
The frequency increases by $20\%$.
Solution by Sreeraj P, M.Sc Physics