CH 24-1

A changing magnetic field generates an electric field. A changing electric field generates a magnetic field. Overview

Electromagnetic Wave An accelerating charged particle creates a changing electric field which creates a changing magnetic field. This propagating “disturbance” in the electric field is an electromagnetic wave.

James Clerk Maxwell In 1864, Maxwell published his theory showing that the propagation of an electromagnetic wave in a vacuum has a speed:

Ramifications Light is an electromagnetic wave. Direction of propagation is given by the right-hand rule with your fingers in the direction of E, your palm facing B, and your thumb in the direction of propagation. Light travels at a finite speed.

Example How long does it take for light to travel from Sun to Earth, if Earth is 1.5 x m from Sun?

Poll What does the blue vector represent? 1.E-field 2.B-field 3.Direction of propagation (k)

If an electromagnetic wave is traveling directly out of the screen, which of the following shows the directions that the electric (in red) and magnetic (in blue) fields that a point P along this path can have at a particular instant? (Assume there are no background fields present.) A. B. C.   D. E.

Sinusoidal Electromagnetic Wave

Electromagnetic Spectrum

Wavelength and Frequency Wavelength and frequency are inversely proportional.

Example A certain FM radio station broadcasts at 88.5 MHz. What is the wavelength of the radio wave that it broadcasts?