A radar sends an electromagnetic signal of electric field E 0 = 2 . 25 V m - 1 and magnetic field B 0 = 1 . 5 × 10 - 8 T which strikes a target on line of sight at a distance of 3 km in a medium. After that, a part of signal (echo) reflects back towards the radar with same velocity and by same path. If the signal was transmitted at time t = 0 from radar, then after how much time echo will reach to the radar?

Question

A radar sends an electromagnetic signal of electric field E 0 = 2 . 25 V m - 1 and magnetic field B 0 = 1 . 5 × 10 - 8 T which strikes a target on line of sight at a distance of 3 km in a medium. After that, a part of signal (echo) reflects back towards the radar with same velocity and by same path. If the signal was transmitted at time t = 0 from radar, then after how much time echo will reach to the radar?, 2 . 0 × 10 - 5 s, 4 . 0 × 10 - 5 s, 1 . 0 × 10 - 5 s, 8 . 0 × 10 - 5 s

MARKS App · Accepted Answer

The speed of light is given by, c = E 0 B 0 = 2 . 25 1 . 5 × 10 - 8 = 1 . 5 × 10 8 m s - 1 Therefore, time taken for the echo will be, t = 2 d c = 6 × 10 3 1 . 5 × 10 8 = 4 × 10 - 5 s

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