A radar sends an electromagnetic signal of electric field \( (E_{0}) = 2.25 \, \text{V/m} \) and magnetic field \( (B_{0}) = 1.5 \times 10^{-8} \, \text{T} \) which strikes a target on line of sight at a distance of \( 3 \, \text{km} \) 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 as transmitted at time \( t = 0 \) from radar, then after how much time echo will reach to the transmitted at time \( t = 0 \) from radar, then after how much time echo will echo to the radar?
