Question

A plane electromagnetic wave travels in free space. Then the ratio of the magnitude of electric and magnetic field at a point is equal to:
A. Inverse of the velocity of the electromagnetic wave
B. Inverse of the energy of electromagnetic wave
C. Velocity of electromagnetic waves.
D. Energy of electromagnetic waves.

Answer 1

Hint: Electricity and magnetism are interconnected with electromagnetic force which lays the foundation of Electromagnetism.

Complete Step by step answer:
We know that the variation of electric field $({E_0})$ and magnetic field ${B_0}$ are mutually perpendicular to each other as well as to the direction of propagation of wave i.e. electromagnetic waves are transverse in nature.

Now, the speed of electromagnetic wave in vacuum is $c = \dfrac{{{E_0}}}{{{B_O}}}$ when we calculate the speed of electromagnetic waves in vacuum by using $\left(c = \dfrac{1}{{\sqrt {{\mu _o}{ \in _o}} }} \right)$. We find out the speed of electromagnetic radiation is equal to the velocity of light in vacuum.
Here $v$ is the velocity of the electromagnetic wave. Therefore,
$v = \dfrac{{{E_O}}}{{{B_O}}}$

Therefore, the ratio of the magnitude of electric and magnetic fields at a point is equal to the velocity of the electromagnetic wave.

Hence the correct option is (C).

Note: An electric field and a magnetic field are perpendicular to each other. A charge in motion generates a magnetic field and also a magnetic field also induces movement of the electric charge.