A report on Light and Electromagnetic spectrum

A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.

The electromagnetic spectrum, with the visible portion highlighted

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.

Beam of sun light inside the cavity of Rocca ill'Abissu at Fondachelli-Fantina, Sicily

Plot of atmospheric opacity for terrestrial to terrestrial transmission showing the molecules responsible for some of the resonances

$Due to refraction, the straw dipped in water appears bent and the ruler scale compressed when viewed from a shallow angle.$

The amount of penetration of UV relative to altitude in Earth's ozone

Hong Kong illuminated by colourful artificial lighting.

$Thomas Young's sketch of a double-slit experiment showing diffraction. Young's experiments supported the theory that light consists of waves.$

Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye.

- Light

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.

- Electromagnetic spectrum

13 related topics with Alpha

Electromagnetic radiation

6 links

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

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.

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.

All of these waves form part of the electromagnetic spectrum.

Infrared

5 links

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.

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

Thermographic image of a snake eating a mouse

Infrared radiation was discovered in 1800 by William Herschel.

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

Beyond infrared is the microwave portion of the electromagnetic spectrum.

Wavelength

5 links

Spatial period of a periodic wave—the distance over which the wave's shape repeats.

Sinusoidal standing waves in a box that constrains the end points to be nodes will have an integer number of half wavelengths fitting in the box.

A standing wave (black) depicted as the sum of two propagating waves traveling in opposite directions (red and blue)

Wavelength is decreased in a medium with slower propagation.

$Refraction: upon entering a medium where its speed is lower, the wave changes direction.$

Separation of colors by a prism (click for animation)

Various local wavelengths on a crest-to-crest basis in an ocean wave approaching shore

A sinusoidal wave travelling in a nonuniform medium, with loss

A wave on a line of atoms can be interpreted according to a variety of wavelengths.

Wavelength of a periodic but non-sinusoidal waveform.

Pattern of light intensity on a screen for light passing through two slits. The labels on the right refer to the difference of the path lengths from the two slits, which are idealized here as point sources.

$Diffraction pattern of a double slit has a single-slit envelope.$

Relationship between wavelength, angular wavelength, and other wave properties.

Examples of waves are sound waves, light, water waves and periodic electrical signals in a conductor.

The name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum.

Ultraviolet

5 links

A 380 nanometer UV LED makes some common household items fluoresce.

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.

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

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.

Signs are often used to warn of the hazard of strong UV sources.

UV damaged polypropylene rope (left) and new rope (right)

IR spectrum showing carbonyl absorption due to UV degradation of polyethylene

A portrait taken using only UV light between the wavelengths of 335 and 365 nanometers.

Aurora at Jupiter's north pole as seen in ultraviolet light by the Hubble Space Telescope.

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.

The electromagnetic spectrum of ultraviolet radiation (UVR), defined most broadly as 10–400 nanometers, can be subdivided into a number of ranges recommended by the ISO standard ISO 21348:

Visible spectrum

5 links

Newton's color circle, from Opticks of 1704, showing the colors he associated with musical notes. The spectral colors from red to violet are divided by the notes of the musical scale, starting at D. The circle completes a full octave, from D to D. Newton's circle places red, at one end of the spectrum, next to violet, at the other. This reflects the fact that non-spectral purple colors are observed when red and violet light are mixed.

Newton's observation of prismatic colors (David Brewster 1855)

How visible light interacts with objects to make them colorful

Approximation of spectral colors on a display results in somewhat distorted chromaticity

Earth's atmosphere partially or totally blocks some wavelengths of electromagnetic radiation, but in visible light it is mostly transparent

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.

Electromagnetic radiation in this range of wavelengths is called visible light or simply light.

Sun

3 links

Star at the center of the Solar System.

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

Measurements from 2005 of solar cycle variation during the previous 30 years

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.

The transition region is not easily visible from Earth's surface, but is readily observable from space by instruments sensitive to the extreme ultraviolet portion of the spectrum.

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

3 links

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

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.

(For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their wavelengths or photon energies: for a more detailed treatment of this and the above frequency ranges, see electromagnetic spectrum.)

Spectrum

1 links

Condition that is not limited to a specific set of values but can vary, without gaps, across a continuum.

Diagram illustrating the electromagnetic spectrum

A Nolan chart of the political spectrum using (red leftism and blue rightism) coding

The word was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism.

As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum.

Fluorescent minerals emit visible light when exposed to ultraviolet light.

Fluorescence

2 links

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

Fluorescence has multiple origins in the tree of life. This diagram displays the origins within actinopterygians (ray finned fish).

Aequoria victoria, biofluorescent jellyfish known for GFP

Fluorescent polka-dot tree frog under UV-light

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.

Telescope

1 links

Optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

The 60-inch Hale (debuted in 1908) considered to be the first modern large research reflecting telescope.

The primary mirror assembly of James Webb Space Telescope under construction. This is a segmented mirror and its coated with Gold to reflect (orange-red) visible light, through near-infrared to the mid-infrared

Modern telescopes typically use CCDs instead of film for recording images. This is the sensor array in the Kepler spacecraft.

A 1.2-meter (47 in) reflecting telescope

The Very Large Array at Socorro, New Mexico, United States.

Einstein Observatory was a space-based focusing optical X-ray telescope from 1978.

The Compton Gamma Ray Observatory is released into orbit by the Space Shutte in 1991, and it would operate until the year 2000

The reflectors of HEGRA detect flashes of light in the atmosphere, thus detecting high energy particles

A diagram of the electromagnetic spectrum with the Earth's atmospheric transmittance (or opacity) and the types of telescopes used to image parts of the spectrum.

Six views of the Crab nebula supernova remnant, viewed at different wavelengths of light by various telescopes

The Five-hundred-meter Aperture Spherical radio Telescope in Guizhou, China, is the world's largest filled-aperture radio telescope

The word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.

Optical telescopes, using visible light