Given
RADAR’s sound transmission speed is \(3\times {{10}^{8}}\)m/ s.
The signal’s transmission distance = 300 km = 300000 meters
The signal travels twice, thus the distance is computed twice when it is broadcast and when it is received by the RADAR.
The signal covers a total distance of \(2\times 300000\) meters.
The time it takes to receive the signal after it has been reflected by the plane is
t=d/s
t= \(\frac{2\times 3\times {{10}^{5}}}{3\times {{10}^{8}}}\)
t = 0.002s
As a result, after reflecting from the aeroplane, the signal is received after 0.002 seconds.