What Are Ultraviolet Rays? Where Do They Come From?

You may have heard that ultraviolet (UV) rays in sunlight can harm our bodies. It is well known that visible sunlight consists of seven colors. However, these seven colors are simply the ones human eyes can see; sunlight contains other wavelengths beyond them. In the context of light rays, color refers to different wavelengths. In visible sunlight, the first color on the spectrum is violet. But just beyond it lies a type of light we cannot see. Scientists call it ultraviolet light. Honeybees and certain animals and birds can see ultraviolet light. Sunlight and light from several other stars contain ultraviolet rays.
Ultraviolet rays are intense; they can burn our skin and damage our eyes. However, not all UV rays from the Sun reach Earth's surface. When they enter Earth's atmosphere, they interact with oxygen to form the ozone layer, which absorbs most of them. This is why the ozone layer is said to protect us. At the same time, our bodies do need a small amount of ultraviolet light: our skin uses UV rays from sunlight to produce Vitamin D. Because UV rays are intense, they are also useful for destroying certain disease-causing bacteria, and scientists have developed UV-producing lamps for this purpose.