A source (S) of sound has frequency 240 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 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 nHz. The value of n is ____.
Answer: 200
Solution
Using the Doppler effect formula: Case 1: f1=(C−vC+v)fs, giving 288=(C−vC+v)240. Case 2: f2=(C+vC−v)fs, giving n=(C+vC−v)240. Multiplying the two equations: 288×n=240×240, yielding n=200.
JEE Advanced · 2024 · 26 May 2024 · Paper 1 · Integer answer