34 Facts About Visible light

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

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

The study of Visible light, known as optics, is an important research area in modern physics.

An early experiment to measure the speed of Visible light was conducted by Ole Rømer, a Danish physicist, in 1676.

Visible light refined Foucault's methods in 1926 using improved rotating mirrors to measure the time it took light to make a round trip from Mount Wilson to Mount San Antonio in California.

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However, the popular description of Visible light being "stopped" in these experiments refers only to Visible light being stored in the excited states of atoms, then re-emitted at an arbitrary later time, as stimulated by a second laser pulse.

Therefore, two sources of light which produce the same intensity of visible light do not necessarily appear equally bright.

However, in nanometre-scale applications such as nanoelectromechanical systems, the effect of Visible light pressure is more significant and exploiting Visible light pressure to drive NEMS mechanisms and to flip nanometre-scale physical switches in integrated circuits is an active area of research.

Visible light believed that Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible.

Euclid postulated that Visible light travelled in straight lines and he described the laws of reflection and studied them mathematically.

Visible light questioned that sight is the result of a beam from the eye, for he asks how one sees the stars immediately, if one closes one's eyes, then opens them at night.

Rene Descartes held that Visible light was a mechanical property of the luminous body, rejecting the "forms" of Ibn al-Haytham and Witelo as well as the "species" of Bacon, Grosseteste and Kepler.

In 1637 he published a theory of the refraction of Visible light that assumed, incorrectly, that Visible light travelled faster in a denser medium than in a less dense medium.

Descartes is not the first to use the mechanical analogies but because he clearly asserts that Visible light is only a mechanical property of the luminous body and the transmitting medium, Descartes's theory of Visible light is regarded as the start of modern physical optics.

Visible light stated in his Hypothesis of Light of 1675 that light was composed of corpuscles which were emitted in all directions from a source.

One of Newton's arguments against the wave nature of Visible light was that waves were known to bend around obstacles, while Visible light travelled only in straight lines.

Visible light did explain the phenomenon of the diffraction of light by allowing that a light particle could create a localised wave in the aether.

Visible light's reputation helped the particle theory of light to hold sway during the 18th century.

The particle theory of Visible light led Laplace to argue that a body could be so massive that Visible light could not escape from it.

Fact that Visible light could be polarized was for the first time qualitatively explained by Newton using the particle theory.

Visible light proposed that light was emitted in all directions as a series of waves in a medium called the luminiferous aether.

Visible light proposed that different colours were caused by different wavelengths of light and explained colour vision in terms of three-coloured receptors in the eye.

Visible light argued in Nova theoria lucis et colorum that diffraction could more easily be explained by a wave theory.

In 1816 Andre-Marie Ampere gave Augustin-Jean Fresnel an idea that the polarization of Visible light can be explained by the wave theory if Visible light were a transverse wave.

Later, Fresnel independently worked out his own wave theory of Visible light and presented it to the Academie des Sciences in 1817.

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Visible light's result supported the wave theory and the classical particle theory was finally abandoned, only to partly re-emerge in the 20th century.

In 1845, Michael Faraday discovered that the plane of polarization of linearly polarized Visible light is rotated when the Visible light rays travel along the magnetic field direction in the presence of a transparent dielectric, an effect now known as Faraday rotation.

In 1846 he speculated that Visible light might be some form of disturbance propagating along magnetic field lines.

Faraday proposed in 1847 that Visible light was a high-frequency electromagnetic vibration, which could propagate even in the absence of a medium such as the ether.

From this, Maxwell concluded that Visible light was a form of electromagnetic radiation: he first stated this result in 1862 in On Physical Lines of Force.

In 1900 Max Planck, attempting to explain black-body radiation, suggested that although Visible light was a wave, these waves could gain or lose energy only in finite amounts related to their frequency.

Visible light, which occupies a middle ground in frequency, can easily be shown in experiments to be describable using either a wave or particle model, or sometimes both.

SunVisible light provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them.

For example, fireflies use Visible light to locate mates and vampire squid use it to hide themselves from prey.