The electric field in a plane electromagnetic wave is given by E z =60 cos (5 x+1.5 × 10 9 t ) V / m . Then expression for the corresponding magnetic field is (here subscripts denote the direction of the field) :

B y =2 × 10 -7 cos (5 x+1.5 × 10 9 t ) T

B x =2 × 10 -7 cos (5 x+1.5 × 10 9 t ) T

B z =60 cos (5 x+1.5 × 10 9 t ) T

B y =60 sin (5 x+1.5 × 10 9 t ) T

Physics · Electrostatics

NEET (UG) 2025 — Question 8

The electric field in a plane electromagnetic wave is given by $E_{z}=60 \cos \left(5 x+1.5 \times 10^{9} t\right) \mathrm{V} / \mathrm{m}$ . Then

expression for the corresponding magnetic field is (here subscripts denote the direction of the field) :

Option A:
$B_{y}=2 \times 10^{-7} \cos \left(5 x+1.5 \times 10^{9} t\right) T$
Correct
Option B:
$B_{x}=2 \times 10^{-7} \cos \left(5 x+1.5 \times 10^{9} t\right) T$
Option C:
$B_{z}=60 \cos \left(5 x+1.5 \times 10^{9} t\right) T$
Option D:
$B_{y}=60 \sin \left(5 x+1.5 \times 10^{9} t\right) T$

$\mathrm{v}=\frac{\omega}{\mathrm{k}}=\frac{1.5 \times 10^{9}}{5}=3 \times 10^{8} \mathrm{~m} / \mathrm{s}$

$\mathrm{B}_{0}=\frac{\mathrm{F}_{0}}{\mathrm{v}}=\frac{60}{3 \times 10^{8}}=20 \times 10^{-8}=2 \times 10^{-7} \mathrm{~T}$

$\mathrm{B}_{\mathrm{y}}=2 \times 10^{-7} \cos \left(5 \mathrm{x}+1.5 \times 10^{9} \mathrm{t}\right) \mathrm{T}$

Answer key and solution verified before publishing.

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