Question

A RADAR sends a signal to an aeroplane at a distance 300 km away, with a speed of 3 x 10 8
ms -1 . After how much time is the signal received back after reflecting from the aeroplane?

Answer 1

Explanation:

Speed of sound transmitted from RADAR = 3 × 108 m/s

Distance at which the signal is transmitted = 300 km =300000m

Since, the signal travells twice, that is, when

transmitted and when it is being received by the RADAR, the distance is calculated twice.

Total distance the signal travels = 2 x 300000 m

Time taken to receive the signal back after reflecting

from the aeroplane

t =d/s

t = 23 x 105 3 x 108

t = 0.002 sec

Thus, after 0.002 s, the signal is received back after

reflecting from the deroplane.