JEE Advanced 2024 · Paper 1 · Physics Q11

← JEE Advanced 2024 · Paper 1

PhysicsInteger+4Question 28 of 51

A source (S) of sound has frequency $240\,\mathrm{Hz}$ . When the observer (O) and the source move towards each other at a speed $v$ with respect to the ground (as shown in Case 1 in the figure), the observer measures the frequency of the sound to be $288\,\mathrm{Hz}$ . However, when the observer and the source move away from each other at the same speed $v$ with respect to the ground (as shown in Case 2 in the figure), the observer measures the frequency of sound to be $n\,\mathrm{Hz}$ . The value of $n$ is _____.

Two cases on a straight line, source S on the left and observer O on the right, joined by a dashed line. Case 1: S moves to the right (towards O) with speed v and O moves to the left (towards S) with speed v. Case 2: S moves to the left (away from O) with speed v and O moves to the right (away from S) with speed v.

Your answer

Answer and worked solution

Official answer: 200

Let the speed of sound be $c$ .

Approaching: $288 = 240\,\dfrac{c+v}{c-v} \implies \dfrac{c+v}{c-v} = 1.2$ .

Receding: $n = 240\,\dfrac{c-v}{c+v} = \dfrac{240}{1.2} = 200$ .

Topics:Doppler effect

← Previous question Next question →

JEE Advanced 2024 · Paper 1, Physics question 11