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JEE MAIN 2021
16-03-2021 S2
Question
Two identical antennas mounted on identical towers are separated from each other by a distance of 45 km. What should nearly be the minimum height of receiving antenna to receive the signals in line of sight ? (Assume radius of earth is 6400 km)
Select the correct option:
A
19.77 m
B
39.55 m
C
79.1 m
D
158.2 m
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
$\begin{aligned} & \mathrm{D}=2 \sqrt{2 \mathrm{Rh}} \\ & \mathrm{h}=\frac{\mathrm{D}^2}{8 \mathrm{R}}=\frac{45^2}{8 \times 6400} \mathrm{~km} \cong 39.55 \mathrm{~m}\end{aligned}$
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