QJEEM12Phb6b3: JEE Main 2012 Physics - Class 12 JEEM12Phb6b3 Solution: An electromagnetic wave in vacuum has the electric and magnetic …

Question

Verified Solution • 2025–26 Session moderate

An electromagnetic wave in vacuum has the electric and magnetic field

\mathop E\limits^ \to

and

\mathop B\limits^ \to

, which are always perpendicular to each other. The direction of polarization is given by

\mathop X\limits^ \to

and that of wave propagation by

\mathop k\limits^ \to

. Then

A $\mathop X\limits^ \to ||\mathop B\limits^ \to$ and $\mathop X\limits^ \to ||\mathop B\limits^ \to \times \mathop E\limits^ \to$
B $\mathop X\limits^ \to ||\mathop E\limits^ \to$ and $\mathop k\limits^ \to ||\mathop E\limits^ \to \times \mathop B\limits^ \to$
C $\mathop X\limits^ \to ||\mathop B\limits^ \to$ and $\mathop k\limits^ \to ||\mathop E\limits^ \to \times \mathop B\limits^ \to$
D $\mathop X\limits^ \to ||\mathop E\limits^ \to$ and $\mathop k\limits^ \to ||\mathop B\limits^ \to \times \mathop E\limits^ \to$

Accepted Answer

as The

E.M.

wave are transverse in nature i.e.,

= {{\overrightarrow k \times \overrightarrow E } \over {\mu \omega }} = \overrightarrow H \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,...\left( i \right)

where

\overrightarrow H = {{\overrightarrow B } \over \mu }

and

{{\overrightarrow k \times \overrightarrow H } \over {\omega \varepsilon }} = - \overrightarrow E \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,...\left( {ii} \right)

\overrightarrow k

is

\bot \,\,\overrightarrow H

and

\overrightarrow k

is also

\bot

to

\overrightarrow E

or In other words

\overrightarrow X ||\overrightarrow E

and

\overrightarrow k ||\overrightarrow E \times \overrightarrow B

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