Q 11-14-050JEE MainJEE Main 2023 (29 Jan, Shift 1)Medium
A person observes two moving trains, $A$ reaching the station and $B$ leaving the station with equal speed of $30\ \text{m s}^{-1}$. If both trains emit sounds with frequency $300\ \text{Hz}$ (speed of sound $330\ \text{m s}^{-1}$), the approximate difference of frequencies heard by the person will be
Answer: (B) $55\ \text{Hz}$
Approaching source: $f_A=300\times\dfrac{330}{330-30}=330\ \text{Hz}$.
Receding source: $f_B=300\times\dfrac{330}{330+30}=275\ \text{Hz}$.
Difference $=330-275=55\ \text{Hz}$.
Solution by Sreeraj P, M.Sc Physics