Medium MCQ +4 / -1 PYQ · JEE Mains 2022

If Electric field intensity of a uniform plane electromagnetic wave is given as $$E = - 301.6\sin (kz - \omega t){\widehat a_x} + 452.4\sin (kz - \omega t){\widehat a_y}{V \over m}$$. Then magnetic intensity 'H' of this wave in Am$-$1 will be :

[Given : Speed of light in vacuum $c = 3 \times {10^8}$ ms$-$1, Permeability of vacuum ${\mu _0} = 4\pi \times {10^{ - 7}}$ NA$-$2]

  1. A $+ 0.8\sin (kz - \omega t){\widehat a_y} + 0.8\sin (kz - \omega t){\widehat a_x}$
  2. B $$ + 1.0 \times {10^{ - 6}}\sin (kz - \omega t){\widehat a_y} + 1.5 \times {10^{ - 6}}(kz - \omega t){\widehat a_x}$$
  3. C $- 0.8\sin (kz - \omega t){\widehat a_y} - 1.2\sin (kz - \omega t){\widehat a_x}$ Correct answer
  4. D $$ - 1.0 \times {10^{ - 6}}\sin (kz - \omega t){\widehat a_y} - 1.5 \times {10^{ - 6}}\sin (kz - \omega t){\widehat a_x}$$

Solution

<p>$$\overrightarrow E = - 301.6\sin (kz - \omega t){\widehat a_x} + 452.4\sin (kz - \omega t){\widehat a_y}$$</p> <p>${E_{0x}} = 301.6$</p> <p>${E_{0y}} = + 452.4$</p> <p>${E_0} = \sqrt {E_{0x}^2 + E_{0y}^2}$</p> <p>Now, $${{{E_0}} \over {{B_0}}} = C \Rightarrow {B_0} = {{{E_0}} \over C} = {{\sqrt {E_{0x}^2 + E_{0y}^2} } \over C}$$</p> <p>Also, $$\widehat B = \widehat C \times \widehat E \Rightarrow \widehat k \times {{({E_{0x}}\widehat i + {E_{0y}}\widehat j)} \over {\sqrt {E_{0x}^2 + E_{0y}^2} }}$$</p> <p>$$\widehat B = {{ - {E_{0x}}\widehat j - {E_{0y}}\widehat i} \over {\sqrt {E_{0x}^2 + E_{0y}^2} }}$$</p> <p>$$\overrightarrow B = - {{{E_{0x}}} \over C}\sin (kz - \omega t){\widehat a_y} - {{{E_{0y}}} \over C}\sin (kz - \omega t){\widehat a_x}$$</p> <p>$\overrightarrow H = {{\overrightarrow B } \over {{\mu _0}}}$</p> <p>$$\overrightarrow H = - {{{E_{0x}}} \over {{\mu _0}C}}\sin (kz - \omega t){\widehat a_y} - {{{E_{0y}}} \over {{\mu _0}C}}\sin (kz - \omega t){\widehat a_x}$$</p>

About this question

Subject: Physics · Chapter: Electromagnetic Waves · Topic: Maxwell's Equations

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