General Study Guide - Ontario Police College

Fluorescence Techniques and Chemical Development of Latent Prints
Light is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human
eye (about 400–700 nm), or perhaps 380–750 nm. [1] In physics, the term light sometimes refers to
electromagnetic radiation of any wavelength, whether visible or not.
Three primary properties of light are:
Intensity
Frequency or wavelength
Polarization
Light's Place in the Electromagnetic Spectrum
The electromagnetic spectrum is the complete range of electromagnetic waves on a continuous
distribution from a very low range of frequencies and energy levels, with a correspondingly long
wavelength, to a very high range of frequencies and energy levels, with a correspondingly short
wavelength. Included on the electromagnetic spectrum are radio waves and microwaves; infrared,
visible, and ultraviolet light; x rays, and gamma rays. Each of these occupies a definite place on the
spectrum but the divisions between them are not firm: in keeping with the nature of a spectrum,
one band simply "blurs" into another.
Over the breadth of the electromagnetic spectrum, wavelengths get much shorter, and frequencies
much greater. The low energy side of the visible spectrum is red, the light with the longest
wavelength. Infrared light and microwaves, not visible to the human eye, are even lower in energy
(and even longer in wavelength). The high energy or short wavelength side of the spectrum is
blue/violet. Ultraviolet is even higher energy, while x-rays and gamma rays are higher still, with
even shorter wavelengths.
Between infrared and ultraviolet light is the region of visible light: the six colors that make up
much of the world we know. Each has a specific range and frequency, and together they occupy an
extremely narrow band of the electromagnetic spectrum - from 700 down to 400 nm in wavelength.
To compare its frequency range to that of the entire spectrum, for instance, is the same as
comparing 3.2 to 100 billion
NOTE - The human eye can generally detect no more than 16 – 32 various shades of gray.