Overview
Ultraviolet (UV) radiation occupies a unique niche in the electromagnetic spectrum, with wavelengths shorter than visible light (400–700 nm) but longer than X-rays (0.01–10 nm). It spans 100–400 nanometers, divided into three categories: UVA (315–400 nm), UVB (280–315 nm), and UVC (100–280 nm). The shortest UV wavelengths (10–100 nm) are termed extreme ultraviolet (EUV), overlapping with soft X-rays in properties. UV constitutes ~10% of the Sun’s total electromagnetic output, driving critical biological and chemical processes on Earth.UV radiation originates from both natural and artificial sources. Solar UV is the most familiar, but human-made sources like electric arcs, mercury-vapor lamps, tanning beds, and black lights also emit UV. While UV is essential for vitamin D synthesis in humans, excessive exposure can cause skin damage, cancer, and ecological harm. Conversely, it is harnessed for sterilization, fluorescence, and analytical techniques.
History/Background
UV radiation was discovered in 1801 by German physicist Johann Wilhelm Ritter, who detected invisible rays beyond the violet end of the visible spectrum using silver chloride, which darkened under UV exposure. The 19th and 20th centuries saw rapid advancements: in 1928, Friedrich Merkel linked UV exposure to skin cancer in animals, while in the 1930s, Auguste Piccard and Fritz Zwicky studied UV’s atmospheric effects. The ozone layer’s role in absorbing harmful UVC (100–280 nm) was elucidated in the 1930s, leading to the 1970s discovery of ozone depletion by chlorofluorocarbons (CFCs).Artificial UV sources emerged in the 20th century. Mercury-vapor lamps, developed in the 1930s, became vital for UV curing and sterilization. Tanning lamps gained popularity in the 1960s, despite growing health concerns. The UV index, a global scale measuring UV intensity, was introduced in 1994 by the World Health Organization (WHO) and World Meteorological Organization (WMO) to warn the public about sun exposure risks.
