Session 1, Page 3: Visible Light and the Electromagnetic Spectrum


To understand how a prism works, we must first know more about light. Visible light is a form of energy referred to as electromagnetic radiation. Electromagnetic radiation is produced by the constant oscillation of electrons in orbit around the nucleus of an atom. The frequency or speed of this oscillation determines the energy level of the radiation. High frequency, short-wavelength radiation has a higher energy level than low frequency, long wavelength radiation. The electromagnetic spectrum is a continuum of wavelengths, from zero to infinity. Visible light is a narrow range of wavelengths of the electromagnetic spectrum. The only region in the entire electromagnetic spectrum that our eyes are sensitive to is the visible region.

	Figure 3 The entire range of all the various kinds of radiation; light (or the visible spectrum) comprises just one small segment of this much broader spectrum. Courtesy of STSCI

The colors in the visible light spectrum have different wavelengths. These wavelengths are extremely small! Wavelengths are typically measured in nanometers (nm). A nanometer is 10 ^-9 meters. That's 0.000000001 meters.

As you can see from Figure 3, red has the longest wavelengths and violet has the shortest.

Figure 4
Wavelengths of light in the visible spectrum.

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