Visual Sciences

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Munsell color system. The Munsell color system, showing: a circle of hues at value 5 chroma 6; the neutral values from 0 to 10; and the chromas of purple-blue (5PB) at value 5.

Munsell color system

Several earlier color order systems had placed colors into a three-dimensional color solid of one form or another, but Munsell was the first to separate hue, value, and chroma into perceptually uniform and independent dimensions, and was the first to systematically illustrate the colors in three-dimensional space.[1] Munsell’s system, particularly the later renotations, is based on rigorous measurements of human subjects’ visual responses to color, putting it on a firm experimental scientific basis.

Because of this basis in human visual perception, Munsell’s system has outlasted its contemporary color models, and though it has been superseded for some uses by models such as CIELAB (L*a*b*) and CIECAM02, it is still in wide use today.[2] Microwave. The atmospheric attenuation of microwaves in dry air with a precipitable water vapor level of 0.001 mm.


The downward spikes in the graph correspond to frequencies at which microwaves are absorbed more strongly. The right half of this graph includes the lower ranges of infrared by some standards Microwaves are a form of electromagnetic radiation with wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz.[1][2] This broad definition includes both UHF and EHF (millimeter waves), and various sources use different boundaries. In all cases, microwave includes the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum, with RF engineering often putting the lower boundary at 1 GHz (30 cm), and the upper around 100 GHz (3 mm). The prefix "micro-" in "microwave" is not meant to suggest a wavelength in the micrometer range. Radio waves. Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light.

Radio waves

Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths ranging from 1 millimeter (0.039 in) to 100 kilometers (62 mi). Like all other electromagnetic waves, they travel at the speed of light. Naturally occurring radio waves are made by lightning, or by astronomical objects. Wavelength. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths.[6] Examples of wave-like phenomena are sound waves, light, and water waves.


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. Water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary. Wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves.

Electromagnetic radiation. The electromagnetic waves that compose electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields.

Electromagnetic radiation

This diagram shows a plane linearly polarized EMR wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane. The two types of fields in EMR waves are always in phase with each other with a fixed ratio of electric to magnetic field intensity. Electromagnetic radiation (EM radiation or EMR) is a form of radiant energy, propagating through space via electromagnetic waves and/or particles called photons. In a vacuum, it propagates at a characteristic speed, the speed of light, normally in straight lines.

Terahertz radiation. Terahertz waves lie at the far end of the infrared band, just before the start of the microwave band.

Terahertz radiation

In physics, terahertz radiation, also called submillimeter radiation, terahertz waves, tremendously high frequency,[1] T-rays, T-waves, T-light, T-lux, or THz, are electromagnetic waves within the ITU-designated band of frequencies from 0.3 to 3 terahertz (THz). The term applies to electromagnetic radiation with frequencies between the high-frequency edge of the millimeter wave band, 300 gigahertz (3×1011 Hz), and the low frequency edge of the far-infrared light band, 3000 GHz (3×1012 Hz). Corresponding wavelengths of radiation in this band range from 1 mm to 0.1 mm (or 100 μm) Because terahertz radiation begins at a wavelength of one millimeter and proceeds into shorter wavelengths, it is sometimes known as the submillimeter band, and its radiation as submillimeter waves, especially in astronomy.

Colour Music. Visible spectrum. The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye.

Visible spectrum

Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm.[1] In terms of frequency, this corresponds to a band in the vicinity of 430–790 THz. The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths.

Munsell_1929_color_solid_transparent. Roy G. Biv. The conventional seven colors of the rainbow symbol Natural rainbows show a continuum of colors.

Roy G. Biv

A rainbow spans a continuous spectrum of colors; the distinct bands are an artifact of human color vision. In Roy G. Biv, the colors are arranged in the order of decreasing wavelengths, with red being 650 nm and violet being about 400 nm. The Roy G.