JEE Main · 2021 · 26 Aug 2021 · Shift 2 · EM Waves

WhatsApp Email

A transmitting antenna at top of a tower has a height of 50 m and the height of receiving antenna is 80 m. What is the range of communication for Line of Sight (LoS) mode? [use radius of earth = 6400 km]

(A)144.1 km
(B)57.28 km✓ Correct
(C)45.5 km
(D)80.2 km

Answer: (B)

Solution

For line-of-sight propagation the range is the sum of the two radio horizons,

d = 2 R h_{T} + 2 R h_{R}

With

R = 6400

km,

h_{T} = 50 m = 0.05

km and

h_{R} = 80 m = 0.08

km,

d = 2 (6400) (0.05) + 2 (6400) (0.08) = 640 + 1024

d = 25.30 + 32.00 = 57.3 km

JEE Main · 2021 · 26 Aug 2021 · Shift 2 · Single correct option

Practise more: all JEE Main PYQs on EM Waves →

More JEE Main questions on EM Waves

The electric field of a plane electromagnetic wave, travelling in an unknown non-magnetic medium is given by,
$E_{y} = 20 sin (3 \times 1 0^{6} x - 4.5 \times 1 0^{14} t) V / m$
(where $x, t$ and ot …
JEE Main 2026View solution →
A laser beam has intensity of $4.0 \times 1 0^{14} W / m^{2}$ . The amplitude of magnetic field associated with beam is ______ T. (Take $ϵ_{0} = 8.85 \times 1 0^{- 12} C^{2} / Nm^{2}$ and $c = 3 \times 1 0^{8} m / s$ )
JEE Main 2026View solution →
An electromagnetic wave of frequency 100 MHz propagates through a medium of conductivity, $σ = 10 mho / m$ . The ratio of maximum conducting current density to maximum displacement current density is ____ .

$[$ Take …
JEE Main 2026View solution →
The equation of the electric field of an electromagnetic wave propagating through free space is given by :
$E = 377 sin (6.27 \times 1 0^{3} t - 2.09 \times 1 0^{- 5} x)$ N/C
The average power of the electromagnetic wave is $(\frac{1}{α})$ W/m $^{2}$ . T …
JEE Main 2026View solution →
The ratio of speeds of electromagnetic waves in vacuum and a medium, having dielectric constant $k = 3$ and permeability of $μ = 2 μ_{0}$ , is ( $μ_{0} =$ permeability of vacuum)
JEE Main 2026View solution →
The electric field of an electromagnetic wave travelling through a medium is given by
$E (x, t) = 25 sin (2.0 \times 1 0^{15} t - 1 0^{7} x) \overset{n}{^}$
then the refractive index of the medium is ______.
(All given measurement are in SI units)
JEE Main 2026View solution →