What is Ultraviolet Light?

Man wondering about UV light


The Discovery of Ultraviolet Light

In 1801, Johann Ritter was investigating energy beyond the visible light spectrum. He already knew that photographic paper turned black more quickly in blue light than in red light. When deciding to expose paper to light beyond violet, which is at the end of the spectrum, he discovered ultraviolet light (literally, “beyond” violet). Learn more in our FAQ: Development of Germicidal Disinfection.

visible light spectrum
Spectrum of Visible Light, from Red (longest) to Violet (shortest)
Johann Wilhelm Ritter
Johann Wilhelm Ritter

The Larger Spectrum of Rays

Ultraviolet light, or UV, is a part of the electromagnetic spectrum along with gamma rays, x-rays, visible light, infrared, microwaves, and radio waves. It has a wavelength ranging from 100 to 400 nanometers. It is shorter than visible light but longer than X-Rays, as shown below.

Diagram of Electromagnetic Spectrum containing ultraviolet light

3 Types of Ultraviolet Light

Ultraviolet light is further classified into 3 wavelength ranges:

  • UV-C, from 100 nanometers (nm) to 280 nm (Referred to as Germicidal Light)
  • UV-B, from 280 nm to 315 nm (Referred to as Sunlight)
  • UV-A, from 315 nm to 400 nm (Referred to as Blacklight)
Classification of ultraviolet light wavelengths

Ultraviolet Light Produced from the Sun

All 3 of these subcategories (UV-A, UV-B, and UV-C) are produced by the sun, and UV rays make up 10% of its radiation output. Fortunately for Earth’s inhabitants, the ozone prevents some UV-B and all UV-C rays from getting through. UV-C light is especially harmful to the eyes and skin, but it is germicidal against disease-causing microorganisms, as you can learn in our FAQ on germicidal ultraviolet light.

Learn More & Shop UV Disinfection

Ultraviolet.com is your source for learning about germicidal ultraviolet technology and its many uses for water, liquid, air, and surfaces. Browse the following pages for more information.

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