Distance between the plane and the radar, d = 300 km = 300,000 m
Velocity of radio waves, c = 3 x 108 ms-1
Waves from the radar will travel to the plane and then reflect and travel back
to the receiver of the radar. Hence, the total distance travelled by the waves
is 2d.
∴ 2d = c xt
∴ t = 2d/c
∴ 2 x300000 /3 x108
∴ t = 2 x 10-3 s = 2ms