A SONAR system fixed in a submarine operates at a frequency 40.0kHz. An enemy submarine moves towards the SONAR with a speed of 360 km`h^(-1)`. What is the frequency of sound reflected by the submarine ? Take the speed of sound in water to be 1450 `ms^(-1)`.

Answer

`46 KHz`

Explanation

Apparent frequency
`f' = ((v + v_(0))/(v))f`
`= ((1450 + 100)/(1450)) xx 40 xx 10^(3)`
This frequency is reflected by the enemy submarine (now source) and is observed by `SONAR`(now observer)
`:.` Apparent frequency ,
`f'' = ((v)/(v - v_(S)))f' = ((1450)/(1450 - 100))4.276 xx 10^(4) = 45.9 xx 10^(3) Hz cong 46 KHz`