6 Electromagnetic Waves Free Online FlashCards

What does Gauss’s law relate?

Gauss’s law relates the electric flux through a closed surface to the enclosed charge: $\oint_S \mathbf{E}\cdot d\mathbf{A}=\frac{Q_{\text{enc}}}{\varepsilon_0}$.

What does Gauss’s law for magnetism state?

The net magnetic flux through any closed surface is zero: $\oint_S \mathbf{B}\cdot d\mathbf{A}=0$.

What does Maxwell’s addition to Ampère’s law establish?

A changing electric field can produce a magnetic field, even where no conduction current flows.

What does Faraday’s law say a changing magnetic field produces?

A changing magnetic field produces an electric field.

What determines the speed of electromagnetic waves in vacuum?

In vacuum, electromagnetic waves travel at $c=\frac{1}{\sqrt{\mu_0\varepsilon_0}}$, approximately $3.00\times10^8\ \text{m/s}$.

How are wave speed, frequency, and wavelength related?

Wave speed, frequency, and wavelength satisfy $c=f\lambda$.

What is the orientation of fields in a plane electromagnetic wave?

A plane electromagnetic wave is transverse: its electric field, magnetic field, and direction of travel are mutually perpendicular.

How are the electric and magnetic fields related in a plane wave?

The fields oscillate in phase, and their amplitudes satisfy $E_0=cB_0$.

How can you determine an electromagnetic wave’s travel direction?

The propagation direction follows the right-hand rule for $\mathbf{E}\times\mathbf{B}$.

Do electromagnetic waves require a material medium?

Electromagnetic waves do not need a material medium; they include radio waves, microwaves, and visible light.

What can generate electromagnetic waves?

Accelerating charges can generate electromagnetic waves; one example is electrons oscillating in a transmitting antenna.

What is the electromagnetic energy density in vacuum?

In vacuum, electromagnetic energy density is $u=\frac{1}{2}\varepsilon_0E^2+\frac{B^2}{2\mu_0}$.