Properties of UV Light

Ultraviolet (UV) light, also called ultraviolet radiation or waves, is a type of light that is invisible to the human eye. While humans are unable to see UV light, UV rays have a variety of properties that can affect humans, in both positive and negative ways. It is important to plan outdoor events and landscaping with these properties in mind.

In science, light is described in terms of waves. Much like sound waves, and waves caused by dropping a rock into a calm pool, light is created by waves that travel through the air. The wavelength of any wave is the distance between the peaks of the waves. According to NASA, the visible light spectrum for humans spans from light that has a wavelength of around 400 nanometers (nm) to light with wavelengths around 725 nm. Ultraviolet light has wavelengths below the visible spectrum. Light with wavelengths around 750 or higher is called infrared light and light with wavelengths lower than 400nm are called ultraviolet. According to NASA, the ultraviolet spectrum spans from about 190 nm to 400 nm. Wavelengths below the UV spectrum are called X-rays.

One of the most well-known properties of UV light is that it can cause damage to human skin, resulting in sunburn. Care should be taken to avoid exposure to direct sunlight for prolonged periods of time to prevent the burning effect of UV light. UV light does, however, promote the ability of the body to synthesize vitamin D; so periodic exposure to sunlight is considered healthy. According to the Health Physics Society, UV light can cause the skin to darken or tan and may cause the skin to become tougher over time. Over exposure to UV light is also associated with skin cancer.

UV light can have a variety of damaging effects on the human eye. According to NASA, "High doses of UV light can cause a temporary clouding of the cornea, called 'snow-blindness', and chronic doses have been tentatively linked to the formation of cataracts." Looking directly at the sun can cause permanent damage to the eyes.

UV light has the ability to make certain substances glow and emit visible light. This property of UV light is used in fluorescent lights such as compact fluorescent lamps (CFLs.) CFLs excite a gaseous mixture with electricity which emits UV light. The UV light then excites a fluorescent coating on the bulb that emits visible light. Producing visible light in this manner is significantly more energy efficient than the process used in standard light bulbs. CFLs are often considered "green" or energy-efficient light bulbs. Installing them around the home can potentially save money.