A report on Light, Electromagnetic radiation and Wavelength

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

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.

The electromagnetic spectrum, with the visible portion highlighted

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.

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.

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.

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

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

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.

Wavelength is decreased in a medium with slower propagation.

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

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

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

Hong Kong illuminated by colourful artificial lighting.

Separation of colors by a prism (click for animation)

Electromagnetic spectrum with visible light highlighted

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

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

A sinusoidal wave travelling in a nonuniform medium, with loss

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

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.

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

- Light

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

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

- Electromagnetic radiation

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

- 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

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

4 related topics with Alpha

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.

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.

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.

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

Frequency is an important parameter used in science and engineering to specify the temporal rate of change observed in oscillatory and periodic phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.

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.

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

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.

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

Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction.

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.