STANDARDPhysics-Electromagnetic Waves

STANDARD Physics Wave Propagation MCQ Question

Type: MCQ-conceptual-Medium-Class 12

A plane electromagnetic wave travels in free space along X-direction. If the value of B (in tesla) at a particular point in space and time is 1.2 × 10⁻⁸ k̂, the value of E (in V m⁻¹) at that point is

A

1.2ĵ

B

3.6k̂

C

1.2k̂

D

3.6ĵ

Correct Answer

Option D

Detailed Explanation

The magnitude of E is E = Bc = (1.2 × 10⁻⁸ T) (3 × 10⁸ m s⁻¹) = 3.6 V m⁻¹. B is along Z-direction and the wave propagates along X-direction. Therefore, E should be in a direction perpendicular to both X and Z axes. Using vector algebra E × B should be along X-direction. Since (+ĵ) × (k̂) = ĩ, E is along the Y-direction. Thus, E = 3.6ĵ V m⁻¹.

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