Ncert Exercises & Solutions

A SONAR system fixed in a submarine operates at a frequency 40.0 kHz. An enemy submarine moves towards the SONAR with a speed of 360 km/h. What is the frequency of sound reflected by the submarine? Take the speed of sound in water to be 1450 m/sec.

Given :

Operating frequency of the SONAR system, ν = 40 kHz

Speed of the enemy submarine, v_{e} = 360 km / h = 100 m / s

Speed of sound in water, v = 1450 m / s

The source is at rest and the observer (enemy submarine) is moving

towards it . Hence, the apparent frequency (ν') received and reflected

by the submarine is given by :

\begin{aligned} ν & = (\frac{v + v_{e}}{v}) ν \\ = (\frac{1450 + 100}{1450}) \times 40 = 42 .76 kHz \end{aligned}

The frequency (ν'') received by the SONAR is :

\begin{aligned} ν'' & = (\frac{v}{v + v_{s}}) ν' \end{aligned}

where, ν_{s} = 100 m / s

∴ ν'' = (\frac{1450}{1450 - 100}) \times 42 .76 = 45 .93 kHz

NEET Information

courses

Company

Botany Questions

Chemistry Questions

Physics Questions

Zoology Questions