Question 93: EM waves

Question

A radar sends an electromagnetic signal of electric field (E
0
) = 2.25 V/m and magnetic field (B
0
) = 1.5 $$	imes$$ 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?

Accepted Answer

E
0
= 2.25 V/m
B
0
= 1.5 $$	imes$$ 10
$$-$$8
T
$$ \Rightarrow {{{E_0}} \over {{B_0}}} = 1.5 	imes {10^8}$$ m/s
$$\Rightarrow$$ Refractive index = 2
Distance to be travelled = 6 km
Time taken $$ = {{6 	imes {{10}^3}} \over {1.5 	imes {{10}^8}}} = 4 	imes {10^{ - 5}}$$ s

Answer

2.0 $$	imes$$ 10
$$-$$5
s

Answer

4.0 $$	imes$$ 10
$$-$$5
s

Answer

1.0 $$	imes$$ 10
$$-$$5
s

Answer

8.0 $$	imes$$ 10
$$-$$5
s

EM waves

Choose the correct answer: