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JEE Main 202122 JulyMorning Shift
Exam
JEE Main
Year
2021
Date
22 July
Shift
Morning Shift
Subject
Physics
Chapter
Communication System

JEE Main 2021 · 22 July · Morning Shift · Physics · Communication System

What should be the height of transmitting antenna and the...

What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of 150km?150km ? The average population density around the tower is 2000km−22000{km}^{- 2} and the value of Re=6.5×106m.{R}_{e} = 6 . 5 \times {10}^{6}m .

Options

  1. AHeight =1731m= 1731m
    Population Covered =1413×105= 1413 \times {10}^{5}
  2. BHeight =1241m= 1241m
    Population Covered =7×105= 7 \times {10}^{5}
  3. CHeight =1600m= 1600m
    Population Covered =2×105= 2 \times {10}^{5}
  4. DHeight =1800m= 1800m
    Population Covered =1413×108= 1413 \times {10}^{8}

Correct answer

A. Height =1731m= 1731m
Population Covered =1413×105= 1413 \times {10}^{5}

Step-by-step solution

Radius covered, r=2RHTr = \sqrt{2R{H}_{T}}
150km=2×(6.5×106m)HT150km = \sqrt{2 \times \left(6 . 5 \times {10}^{6}m\right){H}_{T}}
(150km×103)2=2×6.5×106HT{\left(150km \times {10}^{3}\right)}^{2} = 2 \times 6 . 5 \times {10}^{6}{H}_{T}
HT=1731m{H}_{T} = 1731m

Population covered =(πr2)(2000km−2)= \left(\pi{r}^{2}\right)\left(2000{km}^{- 2}\right)
=3.14×(150)2×2000=1413×105= 3 . 14 \times ( 150{)}^{2} \times 2000 = 1413 \times {10}^{5}

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