A report on Light, Speed of light, Refractive index and Polarization (waves)

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

The Lorentz factor γ as a function of velocity. It starts at1 and approaches infinity as v approaches c.

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

Circular polarization on rubber thread, converted to linear polarization

The electromagnetic spectrum, with the visible portion highlighted

Event A precedes B in the red frame, is simultaneous with B in the green frame, and follows B in the blue frame.

$Refraction of a light ray$

The blue dot moves at the speed of the ripples, the phase velocity; the green dot moves with the speed of the envelope, the group velocity; and the red dot moves with the speed of the foremost part of the pulse, the front velocity.

$Thomas Young coined the term index of refraction.$

A "vertically polarized" electromagnetic wave of wavelength λ has its electric field vector E (red) oscillating in the vertical direction. The magnetic field B (or H) is always at right angles to it (blue), and both are perpendicular to the direction of propagation (z).

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

A beam of light is depicted travelling between the Earth and the Moon in the time it takes a light pulse to move between them: 1.255 seconds at their mean orbital (surface-to-surface) distance. The relative sizes and separation of the Earth–Moon system are shown to scale.

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

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

Measurement of the speed of light using the eclipse of Io by Jupiter

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

Hong Kong illuminated by colourful artificial lighting.

Aberration of light: light from a distant source appears to be from a different location for a moving telescope due to the finite speed of light.

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

One of the last and most accurate time of flight measurements, Michelson, Pease and Pearson's 1930–35 experiment used a rotating mirror and a one-mile (1.6 km) long vacuum chamber which the light beam traversed 10 times. It achieved accuracy of ±11 km/s.

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

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

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

Electromagnetic standing waves in a cavity

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

An interferometric determination of length. Left: constructive interference; Right: destructive interference.

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.

Animation showing four different polarization states and three orthogonal projections.

Rømer's observations of the occultations of Io from Earth

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

A circularly polarized wave as a sum of two linearly polarized components 90° out of phase

Hendrik Lorentz (right) with Albert Einstein

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

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

Color pattern of a plastic box showing stress-induced birefringence when placed in between two crossed polarizers.

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

Paths taken by vectors in the Poincaré sphere under birefringence. The propagation modes (rotation axes) are shown with red, blue, and yellow lines, the initial vectors by thick black lines, and the paths they take by colored ellipses (which represent circles in three dimensions).

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

$A stack of plates at Brewster's angle to a beam reflects off a fraction of the s-polarized light at each surface, leaving (after many such plates) a mainly p-polarized beam.$

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

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

Photomicrograph of a volcanic sand grain; upper picture is plane-polarized light, bottom picture is cross-polarized light, scale box at left-center is 0.25 millimeter.

$The principle of many refractometers$

Effect of a polarizer on reflection from mud flats. In the picture on the left, the horizontally oriented polarizer preferentially transmits those reflections; rotating the polarizer by 90° (right) as one would view using polarized sunglasses blocks almost all specularly reflected sunlight.

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

One can test whether sunglasses are polarized by looking through two pairs, with one perpendicular to the other. If both are polarized, all light will be blocked.

A differential interference contrast microscopy image of yeast cells

The effects of a polarizing filter (right image) on the sky in a photograph

Colored fringes in the Embassy Gardens Sky Pool when viewed through a polarizer, due to stress-induced birefringence in the skylight

Circular polarization through an airplane plastic window, 1989

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

All forms of electromagnetic radiation, including visible light, travel at the speed of light.

- Speed of light

The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum and polarization.

- Light

Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature.

- Light

Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids.

- Polarization (waves)

The speed at which light propagates through transparent materials, such as glass or air, is less than c; similarly, the speed of electromagnetic waves in wire cables is slower than c. The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material (

- Speed of light

Even in isotropic media, so-called inhomogeneous waves can be launched into a medium whose refractive index has a significant imaginary part (or "extinction coefficient") such as metals; these fields are also not strictly transverse.

- Polarization (waves)

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

If the electrons emit a light wave which is 270° out of phase with the light wave shaking them, it will cause the wave to travel faster. This is called "anomalous refraction", and is observed close to absorption lines (typically in infrared spectra), with X-rays in ordinary materials, and with radio waves in Earth's ionosphere. It corresponds to a permittivity less than 1, which causes the refractive index to be also less than unity and the phase velocity of light greater than the speed of light in vacuum c (note that the signal velocity is still less than c, as discussed above). If the response is sufficiently strong and out-of-phase, the result is a negative value of permittivity and imaginary index of refraction, as observed in metals or plasma.

- Refractive index

In a vacuum, the components of the electric field propagate at the speed of light, so that the phase of the wave varies in space and time while the polarization state does not.

- Polarization (waves)

The refractive index of a material may depend on the light's frequency, intensity, polarization, or direction of propagation; in many cases, though, it can be treated as a material-dependent constant.

- Speed of light

In some materials, the refractive index depends on the polarization and propagation direction of the light.

- Refractive index

A report on Light, Speed of light, Refractive index and Polarization (waves)

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