In 1873, James Clerk Maxwell proposed that light consists of electromagnetic waves.
According to his theory, an electromagnetic wave has an electric field and magnetic
field components. These two components vibrate in two mutually perpendicular
planes (Figure 1.6). EMR is the emission and transmission of energy in the form of
electromagnetic waves.
Figure 1.6: The electric field and magnetic field components of an
electromagnetic waves
Electromagnetic waves have three primary characteristics: wavelength, frequency
and speed. Wavelength (λ, Greek lambda), is the distance the wave travels during one
cycle (Figure 1.7). It is expressed in meters (m) and often, for very short wavelengths,
in nanometers (nm), picometers (pm), or angstrom (Å). Frequency (ν, Greek letter
nu) is the number of cycles the wave undergoes per second and is expressed in units
of l/second (1/s; also called hertz, Hz).
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