Ultraviolet (UV) light is a type of electromagnetic radiation on the electromagnetic spectrum. The frequency of UV light is higher than that of visible light. This means it has more energy, which makes its wavelength shorter. This increased energy causes chemical effects in many objects — such as skin, plastics, and even some clothing dyes.
One major difference between UV and visible light is its wavelength; UV has a smaller wavelength than visible light. The electromagnetic spectrum is divided into different “bands” depending on wavelength - ultraviolet light is the shortest, while infrared light is the longest. The term “visible light” refers to the part of the spectrum that the human eye can see.
A majority of the UV rays that humans come in contact with the sun. However, other UV light sources also exist. Black lights, mercury lamps, and tanning lights all emit at levels of UV radiation.
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Wavelength and Frequency of UV Rays
Electromagnetic waves work differently. All waves of the same type of frequency travel at the same speed. But their wavelength and frequency differ, depending on the type of wave. The frequency of a wave is measured in Hertz; its unit is Hz.
UV light wavelengths are measured in nanometres, with one nanometre equal to one billionth of a metre. Ultraviolet rays are shorter wavelengths than visible light, which is why we cannot see them when seen naked-eye.
Ultraviolet rays are in the wavelength range from 10 to 400 nanometers (nm). They come in the frequency range of 800 terahertz (THz) to 30 petahertz (PHz). Ultraviolet radiation is usually divided into four regions.
The first region is near, which goes from 400–300 nm.
The second region is in the middle, which is 300–200 nm.
The third region is far, which ranges from 200–100 nm.
The last region is extreme, which goes below 100 nm.
Types of UV Light
UV Rays are separated into three groups: UV-A, UV-B, and UV-C. Each group has a distinct characteristic.
Ultraviolet A (UVA)
Ultraviolet B (UVB):
Ultraviolet C (UVC)
1. 98.7% of the UV light reaching Earth is UVA. It is affected by the ozone.
2. Fading of paints and dyes.
3. UVA causes early ageing of the skin.
4. UVA causes skin cancer called melanoma.
1. 1.3% of the UV reaches the earth’s surface and is highly affected by ozone.
2. For the production of vitamin D, 270-300 nm wavelengths are responsible.
1. UVC rays do not reach the earth’s surface as most of them are absorbed by the atmospheric nitrogen, oxygen, and ozone, and the rest are scattered.
2. UVC causes lesions on the skin.
Use of Ultraviolet Rays
Ultraviolet light has many uses, including treating skin diseases like lupus and vitiligo, but photography is one of its most common uses. The same technology that produces blacklight posters, fluorescence art, sunless tanning solutions, and teeth whitening products also provides us with protection from pests like bed bugs. Here are some of UV light uses in detail:
UV Light in Tanning - Sunburn is a result of too much exposure to dangerous UV light. The body’s natural defence mechanism kicks in and produces a pigment called melanin. The body sends this pigment into neighbouring cells to try and prevent damage. Tanning beds use UV lights that pass electric currents through vaporised mercury to create the sun's rays.
Lamps - Lots of substances can absorb UV light. Some naturally occurring substances like plants and fungi and some man-made substances like synthetic fluorophores will do it too - one of them being fluorescent lamps. When UV light is absorbed, electrons in the material reach a higher energy level before gradually returning to their original position. Each time they do so, they release a small amount of the energy they have absorbed as visible light.
Cancer Treatment - One of the benefits of UVA light is that it can be used to treat skin cancer. Psoralens, or drugs, are given to patients to react to the UVA light and slow the growth of cells on the body. Patients who use this treatment experience great benefits, such as having treatments with lamps similar to tanning beds. There is some risk of burning the skin if not careful, but proper calibration will minimise this risk.
Chemistry - UV lights are used by scientists to examine the chemical structure of a compound. The sensitive machine, called a spectrophotometer, monitors colour changes in UV light radiation to determine how much of a certain compound is present. This process is often used in a variety of industries. For example, it can identify unwanted compounds in water by monitoring a change in colour during drinking water production.
Photography - UV photography is a specialised type of photography that allows photographers to capture images with UV light. Most UV photography is used for medical, scientific and forensic purposes. Nature photographers may take pictures of flowers with UV photography because the human eye can’t see these details. By using UV photography, they can capture only the UV light that hits the camera sensor.