A report on Wavelength and Electromagnetic radiation

The wavelength of a sine wave, λ, can be measured between any two points with the same phase, such as between crests (on top), or troughs (on bottom), or corresponding zero crossings as shown.

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.

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.

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

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.

Wavelength is decreased in a medium with slower propagation.

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.

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

Representation of the electric field vector of a wave of circularly polarized electromagnetic radiation.

Separation of colors by a prism (click for animation)

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

Electromagnetic spectrum with visible light highlighted

A sinusoidal wave travelling in a nonuniform medium, with loss

Rough plot of Earth's atmospheric absorption and scattering (or opacity) of various wavelengths of electromagnetic radiation

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.

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

A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary.

- Wavelength

The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength.

- Electromagnetic radiation

10 related topics with Alpha

Light

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The electromagnetic spectrum, with the visible portion highlighted

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

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

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.

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).

Electromagnetic spectrum

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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

The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.

Visible spectrum

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Portion of the electromagnetic spectrum that is visible to the human eye.

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

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

$A ray of light being refracted in a plastic block.$

Refraction

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Redirection of a wave as it passes from one medium to another.

$A ray of light being refracted in a plastic block.$

$Refraction of light at the interface between two media of different refractive indices, with n2 > n1. Since the phase velocity is lower in the second medium (v2 < v1), the angle of refraction θ2 is less than the angle of incidence θ1; that is, the ray in the higher-index medium is closer to the normal.$

$A pen partially submerged in a bowl of water appears bent due to refraction at the water surface.$

When a wave moves into a slower medium the wavefronts get compressed. For the wavefronts to stay connected at the boundary the wave must change direction.

$A pencil part immersed in water looks bent due to refraction: the light waves from X change direction and so seem to originate at Y.$

$An image of the Golden Gate Bridge is refracted and bent by many differing three-dimensional drops of water.$

$The sun appears slightly flattened when close to the horizon due to refraction in the atmosphere.$

Heat haze in the engine exhaust above a diesel locomotive.

$Water waves are almost parallel to the beach when they hit it because they gradually refract towards land as the water gets shallower.$

The refractive index of materials varies with the wavelength of light, and thus the angle of the refraction also varies correspondingly.

1) Light slows as it travels through a medium other than vacuum (such as air, glass or water). This is not because of scattering or absorption. Rather it is because, as an electromagnetic oscillation, light itself causes other electrically charged particles such as electrons, to oscillate. The oscillating electrons emit their own electromagnetic waves which interact with the original light. The resulting "combined" wave has wave packets that pass an observer at a slower rate. The light has effectively been slowed. When light returns to a vacuum and there are no electrons nearby, this slowing effect ends and its speed returns to c.

Frequency

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Number of occurrences of a repeating event per unit of time.

A pendulum with a period of 2.8 s and a frequency of 0.36 Hz

Diagram of the relationship between the different types of frequency and other wave properties.

Complete spectrum of electromagnetic radiation with the visible portion highlighted

The sound wave spectrum, with rough guide of some applications

For periodic waves in nondispersive media (that is, media in which the wave speed is independent of frequency), frequency has an inverse relationship to the wavelength, λ (lambda).

Visible light is an electromagnetic wave, consisting of oscillating electric and magnetic fields traveling through space.

Wave

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Propagating dynamic disturbance of one or more quantities.

Example of biological waves expanding over the brain cortex, an example of spreading depolarizations.

Wavelength λ, can be measured between any two corresponding points on a waveform

Animation of two waves, the green wave moves to the right while blue wave moves to the left, the net red wave amplitude at each point is the sum of the amplitudes of the individual waves. Note that f(x,t) + g(x,t) = u(x,t)

Sine, square, triangle and sawtooth waveforms.

Amplitude modulation can be achieved through f(x,t) = 1.00×sin(2π/0.10×(x−1.00×t)) and g(x,t) = 1.00×sin(2π/0.11×(x−1.00×t))only the resultant is visible to improve clarity of waveform.

Illustration of the envelope (the slowly varying red curve) of an amplitude-modulated wave. The fast varying blue curve is the carrier wave, which is being modulated.

The red square moves with the phase velocity, while the green circles propagate with the group velocity

A wave with the group and phase velocities going in different directions

Standing wave. The red dots represent the wave nodes

$Light beam exhibiting reflection, refraction, transmission and dispersion when encountering a prism$

$Sinusoidal traveling plane wave entering a region of lower wave velocity at an angle, illustrating the decrease in wavelength and change of direction (refraction) that results.$

Identical waves from two sources undergoing interference. Observed at the bottom one sees 5 positions where the waves add in phase, but in between which they are out of phase and cancel.

Schematic of light being dispersed by a prism. Click to see animation.

A propagating wave packet; in general, the envelope of the wave packet moves at a different speed than the constituent waves.

Animation showing the effect of a cross-polarized gravitational wave on a ring of test particles

One-dimensional standing waves; the fundamental mode and the first 5 overtones.

A two-dimensional standing wave on a disk; this is the fundamental mode.

A standing wave on a disk with two nodal lines crossing at the center; this is an overtone.

In an electromagnetic wave (such as light), coupling between the electric and magnetic fields which sustains propagation of a wave involving these fields according to Maxwell's equations.

Electromagnetic waves, according to their frequencies (or wavelengths) have more specific designations including radio waves, infrared radiation, terahertz waves, visible light, ultraviolet radiation, X-rays and gamma rays.

$In a dispersive prism, material dispersion (a wavelength-dependent refractive index) causes different colors to refract at different angles, splitting white light into a spectrum.$

Dispersion (optics)

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Phenomenon in which the phase velocity of a wave depends on its frequency; sometimes the term chromatic dispersion is used for specificity to optics in particular.

$In a dispersive prism, material dispersion (a wavelength-dependent refractive index) causes different colors to refract at different angles, splitting white light into a spectrum.$

A compact fluorescent lamp seen through an Amici prism

$The variation of refractive index vs. vacuum wavelength for various glasses. The wavelengths of visible light are shaded in grey.$

Although the term is used in the field of optics to describe light and other electromagnetic waves, dispersion in the same sense can apply to any sort of wave motion such as acoustic dispersion in the case of sound and seismic waves, and in gravity waves (ocean waves).

The most familiar example of dispersion is probably a rainbow, in which dispersion causes the spatial separation of a white light into components of different wavelengths (different colors).

one nanometric carbon nanotube, photographed with scanning tunneling microscope

Nanometre

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Unit of length in the metric system, equal to one billionth (short scale) of a metre (0 m).

Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The nanometre is often used to express dimensions on an atomic scale and mostly in the molecular scale.

The nanometre is also commonly used to specify the wavelength of electromagnetic radiation near the visible part of the spectrum: visible light ranges from around 400 to 700 nm.

$A diffraction pattern of a red laser beam projected onto a plate after passing through a small circular aperture in another plate$

Diffraction

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Obstacle or opening.

$A diffraction pattern of a red laser beam projected onto a plate after passing through a small circular aperture in another plate$

Infinitely many points (three shown) along length d project phase contributions from the wavefront, producing a continuously varying intensity θ on the registering plate.

$Thomas Young's sketch of two-slit diffraction for water waves, which he presented to the Royal Society in 1803.$

$Photograph of single-slit diffraction in a circular ripple tank$

$Circular waves generated by diffraction from the narrow entrance of a flooded coastal quarry$

$A solar glory on steam from hot springs. A glory is an optical phenomenon produced by light backscattered (a combination of diffraction, reflection and refraction) towards its source by a cloud of uniformly sized water droplets.$

$2D Single-slit diffraction with width changing animation$

$Numerical approximation of diffraction pattern from a slit of width four wavelengths with an incident plane wave. The main central beam, nulls, and phase reversals are apparent.$

$Graph and image of single-slit diffraction.$

$2-slit (top) and 5-slit diffraction of red laser light$

$Diffraction of a red laser using a diffraction grating.$

$A diffraction pattern of a 633 nm laser through a grid of 150 slits$

A computer-generated image of an Airy disk.

$Computer generated light diffraction pattern from a circular aperture of diameter 0.5 micrometre at a wavelength of 0.6 micrometre (red-light) at distances of 0.1 cm – 1 cm in steps of 0.1 cm. One can see the image moving from the Fresnel region into the Fraunhofer region where the Airy pattern is seen.$

The Airy disk around each of the stars from the 2.56 m telescope aperture can be seen in this lucky image of the binary star zeta Boötis.

$The upper half of this image shows a diffraction pattern of He-Ne laser beam on an elliptic aperture. The lower half is its 2D Fourier transform approximately reconstructing the shape of the aperture.$

$Following Bragg's law, each dot (or reflection) in this diffraction pattern forms from the constructive interference of X-rays passing through a crystal. The data can be used to determine the crystal's atomic structure.$

$Computer generated intensity pattern formed on a screen by diffraction from a square aperture.$

$Generation of an interference pattern from two-slit diffraction.$

$Computational model of an interference pattern from two-slit diffraction.$

$Optical diffraction pattern ( laser), (analogous to X-ray crystallography)$

$Colors seen in a spider web are partially due to diffraction, according to some analyses.<ref>{{cite web|url = http://www.itp.uni-hannover.de/%7Ezawischa/ITP/spiderweb.html|title = Optical effects on spider webs|author = Dietrich Zawischa|access-date = 2007-09-21}}</ref>$

$Diffraction on a sharp metallic edge$

$Diffraction on a soft aperture, with a gradient of conductivity over the image width$

The characteristic bending pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image.

These effects also occur when a light wave travels through a medium with a varying refractive index, or when a sound wave travels through a medium with varying acoustic impedance – all waves diffract, including gravitational waves, water waves, and other electromagnetic waves such as X-rays and radio waves.

Plaque at the Humboldt University of Berlin: "Max Planck, who discovered the elementary quantum of action h, taught here from 1889 to 1928."

Planck constant

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First postulated by Max Planck in 1900 as part of a solution to the ultraviolet catastrophe.

Intensity of light emitted from a black body. Each curve represents behavior at different body temperatures. Planck's constant h is used to explain the shape of these curves.

The divergence of the theoretical Rayleigh–Jeans (black) curve from the observed Planck curves at different temperatures.

He assumed that a hypothetical electrically charged oscillator in a cavity that contained black-body radiation can only change its energy in quantized steps, and that the energies of those steps are proportional to the frequency of the oscillator's associated electromagnetic wave.

For example, green light with a wavelength of 555 nanometres (a wavelength that can be perceived by the human eye to be green) has a frequency of 540 THz (540 Hz).