JEE Main · 2020 · 08 Jan 2020 · Shift 2 · EM Waves

WhatsApp Email

A plane electromagnetic wave of frequency 25 GHz is propagating in vacuum along the z-direction. At a particular point in space and time, the magnetic field is given by

B = 5 \times 1 0^{- 8} \hat{j} T

. The corresponding electric field

E

is (speed of light

c = 3 \times 1 0^{8} ms^{- 1}

)

(A) $- 1.66 \times 1 0^{- 16} \hat{i} V / m$
(B) $- 15 \hat{i} V / m$
(C) $15 \hat{i} V / m$ ✓ Correct
(D) $1.66 \times 1 0^{- 16} \hat{i} V / m$

Answer: (C)

Solution

In an electromagnetic wave the field magnitudes are tied by

E = c B

, so

E = (3 \times 1 0^{8}) (5 \times 1 0^{- 8}) = 15

V/m. The direction follows from

E \times B

pointing along the propagation direction

+ \hat{k}

: with

B

along

+ \hat{j}

, the field must lie along

+ \hat{i}

so that

\hat{i} \times \hat{j} = \hat{k}

. Hence

E = 15 \hat{i}

V/m.

JEE Main · 2020 · 08 Jan 2020 · 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 →