Question

A plane electromagnetic wave travels in free space along X-direction. If the value of $\overrightarrow{B}$ (in tesla) at a particular point in space and time is 1.2×10-8k, the value of $\overrightarrow{E}$ (in V$m^{- 1}$) at that point is:

• A. $1.2\widehat{j}$
• B. $3.6\widehat{j}$
• C. $1.2\widehat{k}$
• D. $3.6\widehat{j}$

Answer 1

Answer: (D)

$3.6\widehat{j}$

Answer 2

: Here, $\overrightarrow{B} = 1.2 \times 10^{- 8}\widehat{k}T$

The magnitude of $\overrightarrow{E}$ is

$E = Bc = (1.2 \times 10^{- 8}T)(3 \times 10^{8}ms^{- 1})$

$= 3.6Vm^{- 1}$

$\overrightarrow{B}$ is along Z – direction and the wave propagates along X – direction. Therefore $\overrightarrow{E}$should be in a direction perpendicular to both X and Z axes. Using vector algebra $\overrightarrow{E} \times \overrightarrow{B}$should be along Z – direction.

Thus, $\overrightarrow{E} = 3.6\widehat{J}Vm^{- 1}$