Q. A source of sound of frequency 90 vibrations/$\sec$ is approaching a stationary observer with a speed equal to $1/10$ the speed of sound. What will be the frequency heard by the observer
A) 80 vibrations/$\sec$
B) 90 vibrations/$\sec$
C) 100 vibrations/$\sec$
D) 120 vibrations/$\sec$
Explanation
(c) $n^{'} = n\left( \frac{v}{v - v_{S}} \right) = 90\left( \frac{v}{v - \frac{v}{10}} \right) = 100\ vibration/sec$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.