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8.Electromagnetic waves
medium
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 (in $\times 10^{-5}\,s$) echo will reach to the radar?
A
$2$
B
$4$
C
$1$
D
$8$
(JEE MAIN-2022)
Solution
$C =\frac{ E _{0}}{ B _{0}}=\frac{2.25}{1.5 \times 10^{- s }}=1.5 \times 10^{8}\,ms ^{-1}$
$t =\frac{6 \times 10^{3}}{1.5 \times 10^{8}}=4 \times 10^{-5}\,s$
Standard 12
Physics
