Direction of Electromagnetic Wave Propagation – Rankers Physics

Properties of EM Waves: Practice Problem & Solution

Assertion (A): An E.M. wave has constantly interchanging electric and magnetic fields, which are perpendicular to each other. Reason (R): The direction of propagation is given by \((\vec{B} \times \vec{E})\).  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Properties of EM Waves. Understanding the underlying formula is key to arriving at the correct answer below:

Electromagnetic waves consist of perpendicular oscillating electric and magnetic fields. The direction of propagation is given by \((\vec{E} \times \vec{B})\) (Poynting vector), not \((\vec{B} \times \vec{E})\). Thus, A is true, but R is false.

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