Pulsed ultraviolet light | Wikipedia audio article
Channel: wikipedia tts
Date: 2019-06-05

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Ultraviolet


00:01:43 1 Visibility
00:02:35 2 Discovery
00:04:15 3 Subtypes
00:07:28 4 Solar ultraviolet
00:09:26 5 Blockers and absorbers
00:11:17 6 Artificial sources
00:11:26 6.1 "Black lights"
00:12:43 6.2 Short-wave ultraviolet lamps
00:14:06 6.3 Incandescent lamps
00:14:41 6.4 Gas-discharge lamps
00:15:38 6.5 Ultraviolet LEDs
00:16:39 6.6 Ultraviolet lasers
00:18:24 6.7 Tunable vacuum ultraviolet (VUV) via sum and difference frequency mixing
00:19:57 6.8 Plasma and synchrotron sources of extreme UV
00:20:42 7 Human health-related effects
00:21:08 7.1 Beneficial effects
00:22:04 7.1.1 Skin conditions
00:22:44 7.2 Harmful effects
00:24:15 7.2.1 Skin damage
00:27:14 7.2.1.1 Sunscreen safety debate
00:29:27 7.2.2 Aggravation of certain skin conditions
00:29:51 7.2.3 Eye damage
00:31:16 8 Degradation of polymers, pigments and dyes
00:32:37 9 Applications
00:34:11 9.1 Photography
00:35:41 9.2 Electrical and electronics industry
00:36:14 9.3 Fluorescent dye uses
00:37:58 9.4 Analytic uses
00:38:06 9.4.1 Forensics
00:38:57 9.4.2 Enhancing contrast of ink
00:39:36 9.4.3 Sanitary compliance
00:40:12 9.4.4 Chemistry
00:41:12 9.5 Material science uses
00:41:21 9.5.1 Fire detection
00:43:00 9.5.2 Photolithography
00:43:57 9.5.3 Polymers
00:45:45 9.6 Biology-related uses
00:45:54 9.6.1 Air purification
00:47:32 9.6.2 Sterilization and disinfection
00:49:43 9.6.3 Biological
00:51:59 9.6.4 Therapy
00:52:50 9.6.5 Herpetology
00:54:38 10 Evolutionary significance
00:55:39 11 See also



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SUMMARY
=======
Ultraviolet  (UV) designates a band of the electromagnetic spectrum with wavelength from 10 nm  to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation is present in sunlight, and contributes about 10% of the total light output of the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules.
Suntan and sunburn are familiar effects of over-exposure of the skin to UV, along with higher risk of skin cancer. Living things on dry land would be severely damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earth's atmosphere. More energetic, shorter-wavelength "extreme" UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground. 
Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans (specifically, UVB). The UV spectrum thus has effects both beneficial and harmful to human health.
The lower wavelength limit of human vision is conventionally taken as 400 nm, so ultraviolet rays are invisible to humans, although some people can perceive light at slightly shorter wavelengths than this (see below).  Insects, birds, and some mammals can see near-UV (i.e. slightly lower wavelengths than humans can see).