Waves

A car P travelling at \(20 \mathrm{~ms}^{-1}\) sounds its horn at a frequency of \(400 \mathrm{~Hz}\). Another car \(\mathrm{Q}\) is travelling behind the first car in the same direction with a velocity \(40 \mathrm{~ms}^{-1}\).

The frequency heard by the passenger of the car \(\mathrm{Q}\) is approximately [Take, velocity of sound \(=360 \mathrm{~ms}^{-1}\) ]