A report on Wavelength, Light and Refractive index

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.

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

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

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.

The electromagnetic spectrum, with the visible portion highlighted

$Refraction of a light ray$

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

$Thomas Young coined the term index of refraction.$

Wavelength is decreased in a medium with slower propagation.

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

$Diamonds have a very high refractive index of 2.417.$

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

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

$A split-ring resonator array arranged to produce a negative index of refraction for microwaves$

Separation of colors by a prism (click for animation)

Hong Kong illuminated by colourful artificial lighting.

$In optical mineralogy, thin sections are used to study rocks. The method is based on the distinct refractive indices of different minerals.$

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

$Light of different colors has slightly different refractive indices in water and therefore shows up at different positions in the rainbow.$

A sinusoidal wave travelling in a nonuniform medium, with loss

$In a prism, dispersion causes different colors to refract at different angles, splitting white light into a rainbow of colors.$

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

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

$The variation of refractive index with wavelength for various glasses. The shaded zone indicates the range of visible light.$

The colors of a soap bubble are determined by the optical path length through the thin soap film in a phenomenon called thin-film interference.

Wavelength of a periodic but non-sinusoidal waveform.

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

Total internal reflection can be seen at the air-water boundary.

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.

$The power of a magnifying glass is determined by the shape and refractive index of the lens.$

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

$The relation between the refractive index and the density of silicate and borosilicate glasses$

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

$A calcite crystal laid upon a paper with some letters showing double refraction$

Birefringent materials can give rise to colors when placed between crossed polarizers. This is the basis for photoelasticity.

$A gradient-index lens with a parabolic variation of refractive index (n) with radial distance (x). The lens focuses light in the same way as a conventional lens.$

$The principle of many refractometers$

$A handheld refractometer used to measure the sugar content of fruits$

A differential interference contrast microscopy image of yeast cells

In optics, the refractive index ( refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium.

- Refractive index

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

The refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is v = c/n, and similarly the wavelength in that medium is λ = λ0/n, where λ0 is the wavelength of that light in vacuum.

- Refractive index

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

- Wavelength

For electromagnetic waves the speed in a medium is governed by its refractive index according to

- Wavelength

where θ1 is the angle between the ray and the surface normal in the first medium, θ2 is the angle between the ray and the surface normal in the second medium and n1 and n2 are the indices of refraction, n = 1 in a vacuum and n > 1 in a transparent substance.

- Light

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

Refraction

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

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

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

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.

For light, refraction follows Snell's law, which states that, for a given pair of media, the ratio of the sines of the angle of incidence θ1 and angle of refraction θ2 is equal to the ratio of phase velocities (v1 / v2) in the two media, or equivalently, to the refractive indices (n2 / n1) of the two media.

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