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JEE Main 202116 MarchEvening Shift

Exam: JEE Main
Year: 2021
Date: 16 March
Shift: Evening Shift
Subject: Physics
Chapter: Communication System

JEE Main 2021 · 16 March · Evening Shift · Physics · Communication System

Two identical antennas mounted on identical towers are separated...

Two identical antennas mounted on identical towers are separated from each other by a distance of

45km

. What should nearly be the minimum height of receiving antenna to receive the signals in line of sight ? (Assume radius of earth is

6400km

)

Options

A $19 . 77m$
B $39 . 55m$
C $79 . 1m$
D $158 . 2m$

Correct answer

B. $39 . 55m$

Step-by-step solution

$D = 2\sqrt{2Rh}$

$h = \dfrac{{D}^{2}}{8R} = \dfrac{{45}^{2}}{8 \times 6400}km ≅ 39 . 55m$

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