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Electromagnetic Waves

JEE Main level, single correct, medium

96 of 165

Question 96 of 165

A plane electromagnetic wave, has frequency of $2.0\times {10}^{10}Hz$ and its energy density is $1.02\times {10}^{-8}J{m}^{-3}$ in vacuum. The amplitude of the magnetic field of the wave is close to $\left(\dfrac{1}{4{\pi \epsilon }_{0}}=9\times {10}^{9}\dfrac{{Nm}^{2}}{{C}^{2}}\right)$ and speed of light $=3\times {10}^{8}m{s}^{-1}$ .

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Answer: (B) $160nT$

Energy Denisty

=\dfrac{1}{2}\dfrac{{B}^{2}}{{\mu }_{0}}

B=\sqrt{2\times {\mu }_{0}\times \text{Energy density}}

B=\sqrt{2\times 4\pi \times {10}^{-7}\times 1.02\times {10}^{-8}}=160\times {10}^{-9}=160nT

JEE Main question paper PDF

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JEE Main 2025 Apr 2 Shift 1 question paper

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