Electromagnetic (EM) Waves
Basics of EM waves

The EM spectrum is simply a name that scientists have given to the set of all types of radiation when discussed as a group. Radiation is energy that travels in waves and spreads out over distance. The visible light that comes from a lamp in a house and radio waves that come from a radio station are two types of electromagnetic waves. Other examples are microwaves, infrared light, ultraviolet light, X-rays, and gamma rays.

All EM waves travel at the speed of light in a vacuum and have a characteristic wavelength (λ) and frequency (f), which can be determined by using the following equation:

c = λ x f, where c = the speed of light (3 x 108 m/s)

This formula states that the wavelength of any EM wave traveling in a vacuum, in meters, multiplied by the frequency of that same EM wave, in Hz, always equals the speed of light or 3 x 108 m/s or 186,000 miles per second.

Use Activity 3.3.1c to practice finding either the frequency or the wavelength of an EM wave when the other value is known. When not traveling in a vacuum, the material affects the velocity of an EM wave. This is illustrated in Activity 3.3.1a.

EM waves exhibit the following properties:

  • reflection or bouncing
  • refraction or bending
  • diffraction or spreading around obstacles
  • scattering or being redirected by particles

This will be discussed in greater detail later in this module. Also, the frequency and the wavelength of an EM wave are inversely proportionally to one another, as shown in Figure .

There are a number of properties that apply to all EM waves, including direction, frequency, wavelength, power, polarization, and phase. The properties which were not previously defined are shown in Figure .

This course will focus on these properties as they apply to a portion of the total EM spectrum that includes radio waves and microwaves. These bands are collectively referred to as the RF Spectrum. EM waves are energy in the form of alternating transverse electric and magnetic fields. Learn more about EM fields and polarization in the Interactive Activities below.


Interactive Media Activity

Interactive Activity: Electromagnetic Fields and Polarization

This activity includes a series of animated, graphical explanations of EM fields and polarization.

Interactive Media Activity

Interactive Activity: Propagation of Light in Matter

This activity demonstrates how light slows down through different materials.

Interactive Media Activity

Interactive Activity: Electromagnetic Calculator

This activity allows students to enter values for frequency and wavelength to calculate the speed of light.

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