Q.
An Indian submarine and an enemy submarine move towards each other during maneuvers in motionless water in the Indian ocean. The Indian submarine moves at $50\ km/h,$ and the enemy submarine at $70\ km/h.$ The Indian sub sends out a sonar signal (sound wave in water) at $1000\ Hz.$ Sonar waves travel at $5500\ km/h.$ What is the frequency detected by the Indian submarine
A) $1.04\ kHz$
B) $2\ kHz$
C) $2.5\ kHz$
D) $4.7\ kHz$
Explanation
(a) Frequency detected by Indian submarine
$n^{'} = n\left( \frac{v + v_{E}}{v - v_{I}} \right)\left( \frac{v + v_{I}}{v - v_{E}} \right) = 1.04\ kHz$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.