8.Electromagnetic waves
easy

If the magnetic field in a plane electromagnetic wave is given by

$\overrightarrow{\mathrm{B}}=3 \times 10^{-8} \sin \left(1.6 \times 10^{3} \mathrm{x}+48 \times 10^{10} \mathrm{t}\right) \hat{\mathrm{j}}\; \mathrm{T}$

then what will be expression for electric field?

A

$\overrightarrow{\mathrm{E}}=\left(9 \sin \left(1.6 \times 10^{3} \mathrm{x}+48 \times 10^{10} \mathrm{t}\right) \hat{\mathrm{k}} \;\mathrm{V} / \mathrm{m}\right)$

B

$\left.\overrightarrow{\mathrm{E}}=\left(3 \times 10^{-8} \sin \left(1.6 \times 10^{3} \mathrm{x}+48 \times 10^{10} \mathrm{t}\right)\right) \hat{\mathrm{i}}\; \mathrm{V} / \mathrm{m}\right)$

C

$\overrightarrow{\mathrm{E}}=\left(60 \sin \left(1.6 \times 10^{3} \mathrm{x}+48 \times 10^{10} \mathrm{t}\right) \hat{\mathrm{k}}\; \mathrm{V} / \mathrm{m}\right)$

D

$\overrightarrow{\mathrm{E}}=\left(3 \times 10^{-8} \sin \left(1.6 \times 10^{3} \mathrm{x}+48 \times 10^{10} \mathrm{t}\right) \hat{\mathrm{j}} \;\mathrm{V} / \mathrm{m}\right)$

(JEE MAIN-2020)

Solution

$\overrightarrow{\mathrm{E}} \times \overrightarrow{\mathrm{B}}=\overrightarrow{\mathrm{C}}=-\hat{\mathrm{i}}$

where $\overrightarrow{\mathrm{B}}$ is along $\hat{\mathrm{j}}$

$\frac{E}{B}=C$

$\mathrm{E}=3 \times 10^{-8} \times 3 \times 10^{8}=9 \mathrm{V} / \mathrm{m}$

Standard 12
Physics

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