WHAT IS AN ELECTROMAGNETIC WAVE?

The waves that we see around us such as ripples in a pond, and oscillations of a rope tied to a support can be defined simply as a disturbance that propagates through a continuous medium at a constant velocity. However, all waves do not require a medium (continuous or discrete) to propagate. There are waves such as electromagnetic waves that propagate without a medium.
In classical physics, an electromagnetic wave is defined as oscillating electric and magnetic fields in a plane (oscillating fields as disturbance) that are perpendicular to the direction of propagation of the wave. Such waves move with the speed of light in a vacuum. Light and any form of radiation is an electromagnetic wave. The Figure 1.1 illustrates electromagnetic waves and ripples in a pond.

FIGURE 1.1 (a) This figure illustrates ripples in a pond as waves that are disturbance in a continuous medium that is water (Credit: Kris Bridgman). (b) This figure illustrates electromagnetic waves as oscillating electric and magnetic fields. Such waves do not require a medium such as water to propagate. (Taken from HyperPhysics website, Credit: Dr. Rod Nave)