A TV transmission tower has a height of $140 \mathrm{~m}$ and the height of the receiving antenna is $40 \mathrm{~m}$. What is the maximum distance upto which signals can be broadcasted from this tower in LOS (Line of Sight) mode? (Given : radius of earth $=6.4 \times 10^{6} \mathrm{~m}$ ).
Correct Option: 1
(1) Maximum distance upto which signal can be broadcasted
$d_{\max }=\sqrt{2 \mathrm{Rh}_{\mathrm{T}}}+\sqrt{2 \mathrm{Rh}_{\mathrm{R}}}$
where $\mathrm{h}_{\mathrm{T}}$ and $\mathrm{h}_{\mathrm{R}}$ are heights of transmission tower and receiving antenna respectively.
Putting values $\mathrm{R}, \mathrm{h}_{\mathrm{T}}$ and $\mathrm{h}_{\mathrm{R}}$
$\mathrm{d}_{\max }=\sqrt{2 \times 6.4 \times 106}[\sqrt{140}+\sqrt{40}]$
or, $\mathrm{d}_{\max } \simeq 65 \mathrm{~km}$