Question

A radar sends an electromagnetic signal of electric field $\left( E _{0}\right)=2.25 \,V / m$ and magnetic field $\left(B_{0}\right)=1.5 \times 10^{-8} T$ which strikes a target on line of sight at a distance of $3\, km$ in a medium. After that, a pail of signal (echo) reflects back towards the radar vitli 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?

• A. $2.0 \times 10^{-5} s$
• B. $4.0 \times 10^{-5} s$
• C. $1.0 \times 10^{-5} s$
• D. $8.0 \times 10^{-5} s$

Answer 1

Answer: (B)

$C =\frac{ E _{0}}{ B _{0}}=\frac{2.25}{1.5 \times 10^{-8}}=1.5 \times 10^{8} ms ^{-1}$
$t =\frac{6 \times 10^{3}}{1.5 \times 10^{8}}=4 \times 10^{-5} s$