JEE Main 201912 Apr, Morning shiftPhysicsMediumOscillations and Waves185× since 2002
A submarine (A) travelling at 18 km/hr is being chased along the line of its velocity by another submarine
(B) travelling at 27 km/hr. B sends a sonar signal of 500 Hz to detect A and receives a reflected sound of
frequency . The value of is close to: (Speed of sound in water =1500 ms^–1)