Answer to Question #277218 in Physics for Ella

Question

How Electromagnetic Waves behave in...

Vacuum?

Optical Medium?

Answer 1

The standard explanation for an electromagnatic wave traveling through vacuum is that a changing electric field creates a magnetic field, and a changing magnetic field creates an electric field, and therefore, a series of changing electric and magnetic fields is created around an oscillating electric charge.

The mechanism of energy transport through a medium involves the absorption and reemission of the wave energy by the atoms of the material. When an electromagnetic wave impinges upon the atoms of a material, the energy of that wave is absorbed. The absorption of energy causes the electrons within the atoms to undergo vibrations. After a short period of vibrational motion, the vibrating electrons create a new electromagnetic wave with the same frequency as the first electromagnetic wave. While these vibrations occur for only a very short time, they delay the motion of the wave through the medium. Once the energy of the electromagnetic wave is reemitted by an atom, it travels through a small region of space between atoms. Once it reaches the next atom, the electromagnetic wave is absorbed, transformed into electron vibrations and then reemitted as an electromagnetic wave. While the electromagnetic wave will travel at a speed of c through the vacuum of interatomic space, the absorption and reemission process causes the net speed of the electromagnetic wave to be less than c.