Question

An em wave is propagating in a medium with a velocity \(\overrightarrow{V} = V\hat{i}\) . The instantaneous oscillating electric field of this em wave is along +y axis. Then the direction of oscillating magnetic field of the em wave will be along

• A. – z direction
• B. – y direction
• C. + z direction
• D. – x direction

Answer 1

The Correct Option is C

To determine the direction of the oscillating magnetic field in an electromagnetic (EM) wave, we use the properties of EM waves.

1. The wave velocity is given by: \[ \vec{V} = V \hat{i} \] This means the wave propagates along the +x direction.
2. The electric field oscillates along the +y direction: \[ \vec{E} \parallel \hat{j} \]
3. In an EM wave, the direction of propagation is given by: \[ \vec{E} \times \vec{B} = \vec{V} \]
4. Since \( \vec{E} \parallel \hat{j} \) and \( \vec{V} \parallel \hat{i} \), we need: \[ \hat{j} \times \vec{B} = \hat{i} \]
5. Using vector cross product rules: \[ \hat{j} \times \hat{k} = \hat{i} \] Hence, \( \vec{B} \parallel \hat{k} \)

Final Answer: Magnetic field is along \( +z \) direction.