Accelerated charges radiate electromagnetic waves. Choose the correct key features of electromagnetic waves from the following:
(A) The electric field is always parallel to the magnetic field.
(B) The electric and magnetic fields are always normal to the direction in which the wave is travelling.
(C) The electric and magnetic fields sometimes vary sinusoidally.
(D) The electric and magnetic fields vary with the same frequency.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (B) and (D) only
(A) False: $\vec{E} \perp \vec{B}$, not parallel.
(B) True: $\vec{E}$ and $\vec{B}$ are both $\perp$ to direction of propagation.
(C) False: they always vary sinusoidally in free space, not sometimes.
(D) True: $\vec{E}$ and $\vec{B}$ oscillate with same frequency.
Correct options: (B), (D).