Question

In an electromagnetic wave, the magnitude of electric and magnetic fields are 100 V/m and 0.265 A/m. The maximum energy flow is

• (A) 26.5 W/m²
• (B) 36.5 W/m²
• (C) 46.7 W/m²
• (D) 765 W/m²

Answer 1

The Correct Option is A

Explanation:
Given:Electrical field E = 100 V/mMagnetic field B = 0.265 A/mThe energy flow is given by the Poynting vector $\overrightarrow{S}=\overrightarrow{E}\times \overrightarrow{B}$$\Rightarrow S=EB\sin \mathrm{\varnothing }$$\Rightarrow S=EB[\mathrm{\varnothing }={90}^{\circ }$, as $E$ and $B$ are perpendicular to each other]$\Rightarrow S=100V/m\times 0.265A/m$$\Rightarrow S=26.5W/m^2$Hence, the correct option is (A).

Answer 2

The mutually perpendicular time-varying electric and magnetic fields give rise to electromagnetic waves which propagate with the speed of light at a right angle to both electric and magnetic fields.

• Radio waves, Microwaves, Visible light, and X-rays are examples of electromagnetic waves.
• The wavelength of the different types of electromagnetic waves is different.
• An oscillating charge is a source of electromagnetic waves.

Properties of Electromagnetic Waves

The followings are the properties of electromagnetic waves

• They does require any material medium for their propagation.
• They can propagate in a vacuum as well as in a medium.
• Speed of electromagnetic waves in free space or vacuum is 3 x 10⁸ m/s.
• Speed of electromagnetic waves in a medium is given by v = 1/√(μ𝜖). Where μ and 𝜖 are the permeability and permittivity of the medium respectively.
• They are transverse in nature.
• They carry energy as they travel from one point to another point in space.
• The average energy density of electromagnetic wave is given by U_av = (𝜖₀E₀²)/2 = B₀²/2μ₀