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Cha p te r

Velocity, frequency, and wavelength are related by the equation:
c = ƒλ
where c = velocity of light, km/s
ƒ = frequency, Hz
λ = wavelength, m

This equation shows that the frequency of a wave is inversely
proportional to the wavelength—that is, higher-frequency waves
have shorter wavelengths.

2.12.1 Properties of Laser Light
Laser stands for light amplification by stimulated emission of radiation.
Laser light is monochromatic, whereas standard white light consists
of all the colors in the spectrum and is broken into its component
colors when it passes through a standard glass prism (Figs. 1.107
and 1.108).

2.12.2 Essential Laser Components
Laser systems consist of four essential components:

• The active medium
• The excitation mechanism
• The feedback mechanism
• The output coupler

2.12.2.1 The Active Medium
The active medium is the collection of atoms, ions, or molecules in
which stimulated emission occurs. It is in this medium that laser light
is produced. The active medium can be a solid, liquid, gas, or semi-
conductor material. Often, the laser takes its name from that of the

FIGURE 2.107 Standard white light.