PlaneElectromagnetic Waves

Let us summarize the properties of electromagnetic waves as we have described them:

•The solutions of Maxwell’s third and fourth equations are wave- like, with both E and B satisfying a wave equation.

•Electromagnetic waves travel through empty space at the speed of light

•The components of the electric and magnetic fields of plane electromagnetic waves are perpendicular to each other and perpendicular to the direction of wave propagation. We can summarize the latter property by saying that electromagnetic waves are transverse waves.

•The magnitudes of E and B in empty space are related by the expression E/B = c.

•Electromagnetic waves obey the principle of superposition.

Derivation of Equations

Derivation of Equations

EnergyCarried by Electromagnetic

Waves

The rate of flow of energy in an electromagnetic wave is described by a vector S, called the Poynting vector:

EnergyCarried by Electromagnetic

Waves

Momentum and Radiation

Pressure

The Spectrum of

Waves

Remember that all forms of the various types of radiation are produced by the same phenomenon — accelerating charges.

Quick Quiz 10.1

In many kitchens, a microwave oven is used to cook food. The frequency of the microwaves is on the order of 1010 Hz. The wavelengths of these microwaves are on the order of (a)kilometers

(b)meters

(c)centimeters

(d) micrometers.

Quick Quiz 10.2

To maximize the radiation pressure on the sails of a spacecraft using solar sailing, should the sheets be

(a)very black to absorb as much sunlight as possible or

(b)very shiny, to reflect as much sunlight as possible?