A report on Ultraviolet and Light

Levels of ozone at various altitudes (DU/km) and blocking of different bands of ultraviolet radiation: In essence, all UVC is blocked by diatomic oxygen (100–200 nm) or by ozone (triatomic oxygen) (200–280 nm) in the atmosphere. The ozone layer then blocks most UVB. Meanwhile, UVA is hardly affected by ozone, and most of it reaches the ground. UVA makes up almost all UV light that penetrates the Earth's atmosphere.
A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.
A 380 nanometer UV LED makes some common household items fluoresce.
The electromagnetic spectrum, with the visible portion highlighted
Ultraviolet photons harm the DNA molecules of living organisms in different ways. In one common damage event, adjacent thymine bases bond with each other, instead of across the "ladder". This "thymine dimer" makes a bulge, and the distorted DNA molecule does not function properly.
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Sunburn effect (as measured by the UV index) is the product of the sunlight spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths. Sunburn production per milliwatt of radiation intensity is increased by nearly a factor of 100 between the near UV‑B wavelengths of 315–295 nm
Beam of sun light inside the cavity of Rocca ill'Abissu at Fondachelli-Fantina, Sicily
Demonstration of the effect of sunscreen. The man's face has sunscreen on his right side only. The left image is a regular photograph of his face; the right image is of reflected UV light. The side of the face with sunscreen is darker because the sunscreen absorbs the UV light.
Due to refraction, the straw dipped in water appears bent and the ruler scale compressed when viewed from a shallow angle.
Signs are often used to warn of the hazard of strong UV sources.
Hong Kong illuminated by colourful artificial lighting.
UV damaged polypropylene rope (left) and new rope (right)
Pierre Gassendi.
IR spectrum showing carbonyl absorption due to UV degradation of polyethylene
Christiaan Huygens.
A portrait taken using only UV light between the wavelengths of 335 and 365 nanometers.
Thomas Young's sketch of a double-slit experiment showing diffraction. Young's experiments supported the theory that light consists of waves.
Aurora at Jupiter's north pole as seen in ultraviolet light by the Hubble Space Telescope.
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A bird appears on many Visa credit cards when they are held under a UV light source
After a training exercise involving fake body fluids, a healthcare worker's personal protective equipment is checked with ultraviolet light to find invisible drops of fluids. These fluids could contain deadly viruses or other contamination.
A collection of mineral samples brilliantly fluorescing at various wavelengths as seen while being irradiated by UV light.
Effects of UV on finished surfaces in 0, 20 and 43 hours.
A low-pressure mercury vapor discharge tube floods the inside of a hood with shortwave UV light when not in use, sterilizing microbiological contaminants from irradiated surfaces.
Entomologist using a UV light for collecting beetles in Chaco, Paraguay.

Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays.

- Ultraviolet

Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).

- Light
Levels of ozone at various altitudes (DU/km) and blocking of different bands of ultraviolet radiation: In essence, all UVC is blocked by diatomic oxygen (100–200 nm) or by ozone (triatomic oxygen) (200–280 nm) in the atmosphere. The ozone layer then blocks most UVB. Meanwhile, UVA is hardly affected by ozone, and most of it reaches the ground. UVA makes up almost all UV light that penetrates the Earth's atmosphere.

13 related topics with Alpha

Overall

A pseudocolor image of two people taken in long-wavelength infrared (body-temperature thermal) radiation.

Infrared

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A pseudocolor image of two people taken in long-wavelength infrared (body-temperature thermal) radiation.
This false-color infrared space telescope image has blue, green and red corresponding to 3.4, 4.6, and 12 μm wavelengths, respectively.
Plot of atmospheric transmittance in part of the infrared region
Materials with higher emissivity appear closer to their true temperature than materials that reflect more of their different-temperature surroundings. In this thermal image, the more reflective ceramic cylinder, reflecting the cooler surroundings, appears to be colder than its cubic container (made of more emissive silicon carbide), while in fact, they have the same temperature.
Active-infrared night vision: the camera illuminates the scene at infrared wavelengths invisible to the human eye. Despite a dark back-lit scene, active-infrared night vision delivers identifying details, as seen on the display monitor.
Thermography helped to determine the temperature profile of the Space Shuttle thermal protection system during re-entry.
Hyperspectral thermal infrared emission measurement, an outdoor scan in winter conditions, ambient temperature −15 °C, image produced with a Specim LWIR hyperspectral imager. Relative radiance spectra from various targets in the image are shown with arrows. The infrared spectra of the different objects such as the watch clasp have clearly distinctive characteristics. The contrast level indicates the temperature of the object.
Infrared light from the LED of a remote control as recorded by a digital camera
Reflected light photograph in various infrared spectra to illustrate the appearance as the wavelength of light changes.
Infrared hair dryer for hair salons, c. 2010s
IR satellite picture of cumulonimbus clouds over the Great Plains of the United States.
The greenhouse effect with molecules of methane, water, and carbon dioxide re-radiating solar heat
Beta Pictoris with its planet Beta Pictoris b, the light-blue dot off-center, as seen in infrared. It combines two images, the inner disc is at 3.6 μm.
An infrared reflectogram of Mona Lisa by Leonardo da Vinci
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Thermographic image of a snake eating a mouse
Infrared radiation was discovered in 1800 by William Herschel.
Infrared hair dryer for hair salons, c. 2010s

Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light.

Of this energy, 527 watts is infrared radiation, 445 watts is visible light, and 32 watts is ultraviolet radiation.

The electromagnetic spectrum

Electromagnetic spectrum

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Range of frequencies of electromagnetic radiation and their respective wavelengths and photon energies.

Range of frequencies of electromagnetic radiation and their respective wavelengths and photon energies.

The electromagnetic spectrum
A diagram of the electromagnetic spectrum, showing various properties across the range of frequencies and wavelengths
Plot of Earth's atmospheric opacity to various wavelengths of electromagnetic radiation. This is the surface-to-space opacity, the atmosphere is transparent to longwave radio transmissions within the troposphere but opaque to space due to the ionosphere.
Plot of atmospheric opacity for terrestrial to terrestrial transmission showing the molecules responsible for some of the resonances
The amount of penetration of UV relative to altitude in Earth's ozone

This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end.

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Electromagnetic radiation

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In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, propagating through space, carrying electromagnetic radiant energy.

In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, propagating through space, carrying electromagnetic radiant energy.

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Shows the relative wavelengths of the electromagnetic waves of three different colours of light (blue, green, and red) with a distance scale in micrometers along the x-axis.
In electromagnetic radiation (such as microwaves from an antenna, shown here) the term "radiation" applies only to the parts of the electromagnetic field that radiate into infinite space and decrease in intensity by an inverse-square law of power, so that the total radiation energy that crosses through an imaginary spherical surface is the same, no matter how far away from the antenna the spherical surface is drawn. Electromagnetic radiation thus includes the far field part of the electromagnetic field around a transmitter. A part of the "near-field" close to the transmitter, forms part of the changing electromagnetic field, but does not count as electromagnetic radiation.
Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This 3D animation shows a plane linearly polarized wave propagating from left to right. The electric and magnetic fields in such a wave are in-phase with each other, reaching minima and maxima together.
Representation of the electric field vector of a wave of circularly polarized electromagnetic radiation.
James Clerk Maxwell
Electromagnetic spectrum with visible light highlighted
Rough plot of Earth's atmospheric absorption and scattering (or opacity) of various wavelengths of electromagnetic radiation

It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.

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Sun

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Star at the center of the Solar System.

Star at the center of the Solar System.

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Illustration of the Sun's structure, in false color for contrast
Illustration of a proton-proton reaction chain, from hydrogen forming deuterium, helium-3, and regular helium-4.
Illustration of different stars's internal structure, the Sun in the middle has an inner radiating zone and an outer convective zone.
High-resolution image of the Sun's surface taken by the Daniel K. Inouye Solar Telescope (DKIST)
During a total solar eclipse, the solar corona can be seen with the naked eye, during the brief period of totality.
The Sun's transition region taken by Hinode's Solar Optical Telescope
Sunlight and glare seen overlooking from the International Space Station
Once outside the Sun's surface, neutrinos and photons travel at the speed of light
Visible light photograph of sunspot
Measurements from 2005 of solar cycle variation during the previous 30 years
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The size of the current Sun (now in the main sequence) compared to its estimated size during its red-giant phase in the future
The Solar System, with sizes of the Sun and planets to scale. The terrestrial planets are on the right, the gas and ice giants are on the left.
The Trundholm sun chariot pulled by a horse is a sculpture believed to be illustrating an important part of Nordic Bronze Age mythology.
Sol, the Sun, from a 1550 edition of Guido Bonatti's Liber astronomiae.
False-color image taken in 2010 as seen in 30.4-nanometer ultraviolet light wavelength
A false-color of a coronal hole on the Sun forming a question mark (22 December 2017)
A false-color solar prominence erupts in August 2012, as captured by the Solar Dynamics Observatory
The Sun seen from Earth, with glare from the lenses. The eye also see glare when looked towards the Sun directly.
Sun and Immortal Birds Gold Ornament by ancient Shu people. The center is a sun pattern with twelve points around which four birds fly in the same counterclockwise direction, Shang dynasty

It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as light, ultraviolet, and infrared radiation.

Fluorescent minerals emit visible light when exposed to ultraviolet light.

Fluorescence

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Fluorescent minerals emit visible light when exposed to ultraviolet light.
Fluorescent marine organisms
Fluorescent clothes used in black light theater production, Prague
Lignum nephriticum cup made from the wood of the narra tree (Pterocarpus indicus), and a flask containing its fluorescent solution
Matlaline, the fluorescent substance in the wood of the tree Eysenhardtia polystachya
Jablonski diagram. After an electron absorbs a high-energy photon the system is excited electronically and vibrationally. The system relaxes vibrationally, and eventually fluoresces at a longer wavelength.
Fluorescent security strip in a US twenty dollar bill under UV light
Fluorescent coral
Fluorescence has multiple origins in the tree of life. This diagram displays the origins within actinopterygians (ray finned fish).
Fluorescent marine fish
Aequoria victoria, biofluorescent jellyfish known for GFP
Fluorescent polka-dot tree frog under UV-light
Fluorescing scorpion
Fluorescence of aragonite
Fluorescent paint and plastic lit by UV tubes. Paintings by Beo Beyond
Endothelial cells under the microscope with three separate channels marking specific cellular components

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.

A perceptible example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the electromagnetic spectrum (invisible to the human eye), while the emitted light is in the visible region; this gives the fluorescent substance a distinct color that can only be seen when exposed to UV light.

Natural color x-ray photogram of a wine scene

X-ray

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Penetrating form of high-energy electromagnetic radiation.

Penetrating form of high-energy electromagnetic radiation.

Natural color x-ray photogram of a wine scene
Example of a Crookes tube, a type of discharge tube that emitted X-rays
Wilhelm Röntgen
Hand mit Ringen (Hand with Rings): print of Wilhelm Röntgen's first "medical" X-ray, of his wife's hand, taken on 22 December 1895 and presented to Ludwig Zehnder of the Physik Institut, University of Freiburg, on 1 January 1896
Taking an X-ray image with early Crookes tube apparatus, late 1800s. The Crookes tube is visible in center. The standing man is viewing his hand with a fluoroscope screen. The seated man is taking a radiograph of his hand by placing it on a photographic plate. No precautions against radiation exposure are taken; its hazards were not known at the time.
Surgical removal of a bullet whose location was diagnosed with X-rays (see inset) in 1897
Images by James Green, from "Sciagraphs of British Batrachians and Reptiles" (1897), featuring (from left) Rana esculenta (now Pelophylax lessonae), Lacerta vivipara (now Zootoca vivipara), and Lacerta agilis
1896 plaque published in "Nouvelle Iconographie de la Salpetrière", a medical journal. In the left a hand deformity, in the right same hand seen using radiography. The authors named the technique Röntgen photography.
A patient being examined with a thoracic fluoroscope in 1940, which displayed continuous moving images. This image was used to argue that radiation exposure during the X-ray procedure would be negligible.
Chandra's image of the galaxy cluster Abell 2125 reveals a complex of several massive multimillion-degree-Celsius gas clouds in the process of merging.
Phase-contrast X-ray image of spider
X-rays are part of the electromagnetic spectrum, with wavelengths shorter than UV light. Different applications use different parts of the X-ray spectrum.
Ionizing radiation hazard symbol
Attenuation length of X-rays in water showing the oxygen absorption edge at 540 eV, the energy−3 dependence of photoabsorption, as well as a leveling off at higher photon energies due to Compton scattering. The attenuation length is about four orders of magnitude longer for hard X-rays (right half) compared to soft X-rays (left half).
Spectrum of the X-rays emitted by an X-ray tube with a rhodium target, operated at 60 kV. The smooth, continuous curve is due to bremsstrahlung, and the spikes are characteristic K lines for rhodium atoms.
Patient undergoing an x-ray exam in a hospital radiology room.
A chest radiograph of a female, demonstrating a hiatal hernia
Plain radiograph of the right knee
Head CT scan (transverse plane) slice – a modern application of medical radiography
Abdominal radiograph of a pregnant woman, a procedure that should be performed only after proper assessment of benefit versus risk
Each dot, called a reflection, in this diffraction pattern forms from the constructive interference of scattered X-rays passing through a crystal. The data can be used to determine the crystalline structure.
Using X-ray for inspection and quality control: the differences in the structures of the die and bond wires reveal the left chip to be counterfeit.
X-ray fine art photography of needlefish by Peter Dazeley

X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays.

He based it on the electromagnetic theory of light.

The Sun, as seen from low Earth orbit overlooking the International Space Station. This sunlight is not filtered by the lower atmosphere, which blocks much of the solar spectrum.

Sunlight

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The Sun, as seen from low Earth orbit overlooking the International Space Station. This sunlight is not filtered by the lower atmosphere, which blocks much of the solar spectrum.
Sunrise over the Gulf of Mexico and Florida. Taken on 20 October 1968 from Apollo 7.
Sunlight on Mars is dimmer than on Earth. This photo of a Martian sunset was imaged by Mars Pathfinder.
Solar irradiance spectrum at top of atmosphere, on a linear scale and plotted against wavenumber
Sunlight shining through clouds, giving rise to crepuscular rays
Spectrum of the visible wavelengths at approximately sea level; illumination by direct sunlight compared with direct sunlight scattered by cloud cover and with indirect sunlight by varying degrees of cloud cover. The yellow line shows the power spectrum of direct sunlight under optimal conditions. To aid comparison, the other illumination conditions are scaled by the factor shown in the key so they match at about 470 nm (blue light).
Sunlight penetrating through a forest canopy in Germany
Édouard Manet: Le déjeuner sur l'herbe (1862-63)
Téli verőfény ("Winter Sunshine") by László Mednyánszky, early 20th century
Sun bathers in Finland

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light.

When direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat.

Blue, green, and red LEDs in 5 mm diffused cases

Light-emitting diode

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Blue, green, and red LEDs in 5 mm diffused cases
Parts of a conventional LED. The flat bottom surfaces of the anvil and post embedded inside the epoxy act as anchors, to prevent the conductors from being forcefully pulled out via mechanical strain or vibration.
Close-up image of a surface mount LED
A bulb-shaped modern retrofit LED lamp with aluminum heat sink, a light diffusing dome and E27 screw base, using a built-in power supply working on mains voltage
Green electroluminescence from a point contact on a crystal of SiC recreates Round's original experiment from 1907.
A 1962 Texas Instruments SNX-100 GaAs LED contained in a TO-18 transistor metal case
LED display of a TI-30 scientific calculator (ca. 1978), which uses plastic lenses to increase the visible digit size
X-Ray of a 1970s 8-digit LED calculator display
Illustration of Haitz's law, showing improvement in light output per LED over time, with a logarithmic scale on the vertical axis
Blue LEDs
Combined spectral curves for blue, yellow-green, and high-brightness red solid-state semiconductor LEDs. FWHM spectral bandwidth is approximately 24–27 nm for all three colors.
RGB LED
Spectrum of a white LED showing blue light directly emitted by the GaN-based LED (peak at about 465 nm) and the more broadband Stokes-shifted light emitted by the Ce3+:YAG phosphor, which emits at roughly 500–700 nm
LEDs are produced in a variety of shapes and sizes. The color of the plastic lens is often the same as the actual color of light emitted, but not always. For instance, purple plastic is often used for infrared LEDs, and most blue devices have colorless housings. Modern high-power LEDs such as those used for lighting and backlighting are generally found in surface-mount technology (SMT) packages (not shown).
Image of miniature surface mount LEDs in most common sizes. They can be much smaller than a traditional 5mm lamp type LED, shown on the upper left corner.
Very small (1.6×1.6×0.35mm) red, green, and blue surface mount miniature LED package with gold wire bonding details.
High-power light-emitting diodes attached to an LED star base (Luxeon, Lumileds)
RGB-SMD-LED
Composite image of an 11 × 44 LED matrix lapel name tag display using 1608/0603-type SMD LEDs. Top: A little over half of the 21 × 86 mm display. Center: Close-up of LEDs in ambient light. Bottom: LEDs in their own red light.
Simple LED circuit with resistor for current limiting
Daytime running light LEDs of an automobile
Red and green LED traffic signals
LED for miners, to increase visibility inside mines
Los Angeles Vincent Thomas Bridge illuminated with blue LEDs
LED costume for stage performers
LED wallpaper by Meystyle
A large LED display behind a disc jockey
Seven-segment display that can display four digits and points
LED panel light source used in an experiment on plant growth. The findings of such experiments may be used to grow food in space on long duration missions.

A light-emitting diode (LED) is a semiconductor light source that emits light when current flows through it.

Later developments produced LEDs available in visible, ultraviolet (UV), and infrared wavelengths, with high, low, or intermediate light output, for instance white LEDs suitable for room and outdoor area lighting.

Top to bottom: Lights flashing at frequencies, 1 Hz and 2 Hz; that is, at 0.5, 1.0 and 2.0 flashes per second, respectively. The time between each flash – the period T – is given by 1⁄f (the reciprocal of f); that is, 2, 1 and 0.5 seconds, respectively.

Hertz

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Unit of frequency in the International System of Units (SI) and is defined as one cycle per second.

Unit of frequency in the International System of Units (SI) and is defined as one cycle per second.

Top to bottom: Lights flashing at frequencies, 1 Hz and 2 Hz; that is, at 0.5, 1.0 and 2.0 flashes per second, respectively. The time between each flash – the period T – is given by 1⁄f (the reciprocal of f); that is, 2, 1 and 0.5 seconds, respectively.
A sine wave with varying frequency
A heartbeat is an example of a non-sinusoidal periodic phenomenon that may be analyzed in terms of frequency. Two cycles are illustrated.

Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz.

Illustration of the relative abilities of three different types of ionizing radiation to penetrate solid matter. Typical alpha particles (α) are stopped by a sheet of paper, while beta particles (β) are stopped by an aluminum plate. Gamma radiation (γ) is dampened when it penetrates lead. Note caveats in the text about this simplified diagram.

Radiation

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Often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles.

Often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles.

Illustration of the relative abilities of three different types of ionizing radiation to penetrate solid matter. Typical alpha particles (α) are stopped by a sheet of paper, while beta particles (β) are stopped by an aluminum plate. Gamma radiation (γ) is dampened when it penetrates lead. Note caveats in the text about this simplified diagram.
The international symbol for types and levels of ionizing radiation (radioactivity) that are unsafe for unshielded humans. Radiation, in general, exists throughout nature, such as in light and sound.
Some kinds of ionizing radiation can be detected in a cloud chamber.
Graphic showing relationships between radioactivity and detected ionizing radiation
Gamma radiation detected in an isopropanol cloud chamber.
Alpha particle detected in an isopropanol cloud chamber
Electrons (beta radiation) detected in an isopropanol cloud chamber
The electromagnetic spectrum
In electromagnetic radiation (such as microwaves from an antenna, shown here) the term "radiation" applies only to the parts of the electromagnetic field that radiate into infinite space and decrease in intensity by an inverse-square law of power so that the total radiation energy that crosses through an imaginary spherical surface is the same, no matter how far away from the antenna the spherical surface is drawn. Electromagnetic radiation includes the far field part of the electromagnetic field around a transmitter. A part of the "near-field" close to the transmitter, is part of the changing electromagnetic field, but does not count as electromagnetic radiation.

electromagnetic radiation, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ)