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Home  >>  JEEMAIN and NEET  >>  Physics  >>  Class12  >>  Electromagnetic Waves

An object is placed at some distance from a radio station. If the interval between transmission and reception of pulses is $2.66 \times 10^{-2}\: sec$, then the distance is:

$\begin {array} {1 1} (a)\;4000\: km & \quad (b)\;2000\: km \\ (c)\;3000\: km & \quad (d)\;2500\: km \end {array}$


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Time difference between transmission and reception of pulses $= T = 2.66 \times 10^{-2}s$
So, time requires for pulse to travel from station to the object $ = t =\large\frac{T}{2}$$ = \large\frac{2.66 \times 10^{-2}}{ 2}$
$= 1.33 \times 10^{-2}s$
So, distance $= t \times$ speed of radio wave in air,
since radio waves are electromagnetic waves its speed is the speed of light
$= 1.33 \times10^{-2}s \times3 \times10^8m/s = 3990 \: km \sim 4000 \: km$
Ans : (a)


answered Feb 28, 2014 by thanvigandhi_1
edited Oct 3, 2014 by thagee.vedartham

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