Saturation

Saturation refers to the perceived vividness of a colour.

  • When colours are more saturated, our eyes interpret it as a colour’s luminance and chroma. This makes us believe that the colours are actually brighter.
  • As saturation decreases, colours appear dull and washed out until all colour disappears leaving only a grey tone.
  • On many colour wheels, saturation increases from the centre to the edge.

https://en.wikipedia.org/wiki/Colorfulness#Saturation

Scattering

Light scattering takes place when light waves are reflected in random directions at the boundary between two media, or by particles and other irregularities within the medium through which they propagate.

  • Light scattering can be caused by an uneven surface at the boundary between two media or by particles and other irregularities within the medium through which they propagate.

https://en.wikipedia.org/wiki/Scattering

Scattering

Light scattering takes place when light waves are reflected in random directions at the boundary between two media, or by particles and other irregularities within the medium through which they propagate.

  • Light scattering can be caused by an uneven surface at the boundary between two media or by particles and other irregularities within the medium through which they propagate.

Scotopic curve

A scotopic curve is a diagram showing that, at low levels of light, where determining colour differences is difficult, the strongest response of the human eye moves towards blue and violet end of the visible spectrum with less sensitivity towards the red when compared with a photopic curve.

  • Whilst a  scotopic curve describes the response of the human eye to low levels of light a photopic curve is a diagram showing that, in bright light, the strongest response of the human eye is to the colour green with less sensitivity towards the spectral extremes of red and violet.

Secondary colour

A secondary colour is a colour made by mixing two primary colours in a given colour space. The colour space may be produced by an additive colour model that involves mixing different wavelengths of light or by a subtractive colour model that involves mixing pigments or dyes.

  • Secondary colours produced by an additive colour model are quite different from the spectral colours seen in a rainbow.
  • A spectral colour is produced by a single wavelength, or a narrow band of wavelengths, within the visible spectrum.
  • A secondary colour produced by an additive colour model results from superimposing wavelengths of light from different areas of the visible spectrum.
  • For the human eye, the best additive primary colours of light are red, green, and blue.
  • RGB colour can be used to produce an extremely wide range of colour.
  • Because RGB colour involves adding different wavelengths of light together (thus the term “additive colour”), the resulting combinations always appear lighter to an observer.
  • When all three primaries (or for that matter all three secondaries) are combined in equal amounts, the result is white.
  • The RGB secondary colours produced by the addition of light turn out to be the best primary colours for pigments, the mixing of which subtracts light.

Secondary colour

A secondary colour is a colour made by mixing two primary colours in a given colour space. The colour space may be produced by an additive colour model that involves mixing different wavelengths of light or by a subtractive colour model that involves mixing pigments or dyes.

Sine

In mathematics, the sine is a trigonometric function of an angle.

  • The sine of an acute angle is defined in the context of a right angle triangle.
  • For any specified angle, it’s sine is the ratio of the length of the side opposite that angle, to the length of the longest side of the triangle (the hypotenuse).
  • The mathematical notation for sine is sin.

Slow medium

Light travels through different media such as air, glass or water at different speeds. A slow medium is one through which it passes more slowly.

  • Light travels through a vacuum at 299,792 kilometres per second.
  • Light travels through other media at lower speeds. In some media, it travels at a speed which is nearer the speed of light as it passes through a vacuum and in others it travels much more slowly.
  • It is useful to know whether a medium is fast or slow to predict what will happen when light crosses the boundary between one medium and another.
  • so:
    • If light crosses the boundary from a medium in which it travels fast into a material in which it travels more slowly, then it will bend towards the normal.
    • If light crosses the boundary from a medium in which it travels slowly into a material in which it travels more quickly, then the light ray will bend away from the normal.

https://en.wikipedia.org/wiki/Refraction

Solar radiation

Solar radiation is the electromagnetic radiation emitted by the sun.

  • Electromagnetic radiation is a type of energy that is commonly known as light. Detached from its source, it is transported by electromagnetic waves (or by their quanta, particles called photons) and propagates through space.
  • Electromagnetic radiation includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
  • Electromagnetic radiation is sometimes called EM radiation or electromagnetic radiant energy (EMR).
  • All forms of electromagnetic radiation can be described in terms of both waves or particles.
  • All forms of electromagnetic radiation travel at 299,792 kilometres per second in a vacuum.

Spectral colour

A spectral colour is a colour evoked in normal human vision by a single wavelength of visible light, or by a narrow band of adjacent wavelengths.

    • A spectral colour is a hue evoked in normal (trichromatic) human vision by a single wavelength of visible light, or by a narrow band of adjacent wavelengths. This is how we see colour in normal viewing conditions such as sunlight or artificial light.
    • Sunshine is a typical case in so far as it contains nearly all spectral hues.
    • Sunshine has a very broad spectral power distribution and as light strikes surfaces, some wavelengths are absorbed, and others are reflected. The mix of reflected wavelengths results in the non-spectral colours we see.

 

    • A non-spectral colour is any hue that cannot be produced by light of a single wavelength or that does not occur in the visible spectrum (e.g. Magenta).
    • Spectral hues are commonly associated with rainbows, prisms and diagrams showing the colours of the visible spectrum (red to violet). But any medium that reflects or transmits a single wavelength of light produces a spectral colour.
    • Spectral colours can be mimicked by RGB colour. This involves mixing coloured lights tuned to the three spectral primaries, red, green and blue. The resulting colours are not spectral colours because of the resulting mix of wavelengths.
    • The intensity, which is to say, the brightness, of a spectral hue viewed by an observer may alter considerably depending on the situation. For example, a low-intensity orange-yellow may appear brown, and a low-intensity yellow-green may appear olive-green.

 

    • The human eye, and so human perception, is tuned to the visible spectrum and so to all wavelengths that correspond with spectral colours between red and violet.
    • The visible spectrum is the range of wavelengths of the electromagnetic spectrum that correspond with all the different colours we see in the world. We do not see colour when exposed to wavelengths of infrared or ultraviolet light.
    • A spectral colour is a hue corresponding with a single wavelength of visible light, or with a narrow band of adjacent wavelengths.
    • In other situations, spectral hues are called pure hues or monochromatic hues.
    • Spectral colours include all the pure hues associated with a rainbow so are sometimes called rainbow colours.

 

  • Rainbow colours include red, orange, yellow, green, blue and violet but the human eye can distinguish many thousands of other spectral colours between each of these.
  • In a continuous spectrum of wavelengths, separate hues are indistinguishable to the human eye.
  • The fact that we see the distinct bands of colour in a rainbow is an artefact of human colour vision.
  • Spectral colours can be mimicked by RGB colour. This involves mixing coloured lights tuned to the three spectral primaries, red, green and blue.

https://en.wikipedia.org/wiki/Spectral_color

Spectral colour

A spectral colour is a colour evoked in normal human vision by a single wavelength of visible light, or by a narrow band of adjacent wavelengths.

    • A spectral colour is a hue evoked in normal (trichromatic) human vision by a single wavelength of visible light, or by a narrow band of adjacent wavelengths.
    • Sunshine contains nearly all spectral hues.
    • Spectral hues are commonly associated with rainbows, prisms and diagrams showing the colours of the visible spectrum (red to violet). But any medium that reflects or transmits a single wavelength of light produces a spectral colour.
    • Rainbow colours include red, orange, yellow, green, blue and violet but the human eye can distinguish many thousands of other spectral colours between each of these.
    • In a continuous spectrum of wavelengths, separate hues are indistinguishable to the human eye.
    • The intensity, which is to say, the brightness of a spectral hue viewed by an observer may alter considerably depending on the situation. For example, a low-intensity orange-yellow may appear brown, and a low-intensity yellow-green may appear olive-green.
    • Spectral colours can be mimicked by RGB colour. This involves mixing coloured lights tuned to the three spectral primaries, red, green and blue. The resulting colours are not spectral colours because of the resulting mix of wavelengths.
    • Spectral colours are sometimes called spectral hues, pure hues or monochromatic hues.
    • The fact that we see the distinct bands of colour in a rainbow is an artefact of human colour vision.

Spectral power distribution

The spectral power distribution (spectral distribution) of a light or colour stimulus refers to the range, mixture and intensity of wavelengths of light that it produces.

  • A diagram showing the accurate measurement of the spectral power distribution of the light given off (emitted, transmitted, or reflected) by a light source or by a surface provides complete information about that stimulus.
  • The human eye contains three colour receptors (cones), which means that every spectral power distribution is reduced to three sensory quantities that can be described by tristimulus values.
  • Different stimuli can in some cases produce the same colour sensation for an observer. This effect (called metamerism) occurs because each type of cone responds to the distribution of energy across the entire spectral power distribution of a light source.

https://en.wikipedia.org/wiki/Spectral_power_distribution

Spectral power distribution

The spectral power distribution (spectral distribution) of a light or colour stimulus refers to the range, mixture and intensity of wavelengths of light that it produces.

  • A diagram showing the accurate measurement of the spectral power distribution of the light given off (emitted, transmitted, or reflected) by a light source or by a surface provides complete information about that stimulus.
  • The human eye contains three colour receptors (cones), which means that every spectral power distribution is reduced to three sensory quantities that can be described by tristimulus values.
  • Different stimuli can in some cases produce the same colour sensation for an observer. This effect (called metamerism) occurs because each type of cone responds to the distribution of energy across the entire spectral power distribution of a light source.

Spectrum

Definition

When discussing light,  a spectrum is a linear scale of spectral colours organised by wavelength.

Explanation

A spectrum or spectra (plural) are produced naturally when light is refracted by a prism or by rain.

A diagram of spectral colours is usually presented in the form of a spectrum, a linear band organised by wavelength with red at one end and violet at the other.

Spectra are often shown in an elongated form so that as many different gradations of colour can be seen as possible.

Speed of light

The speed (or velocity) of a light wave is a measurement of how far it travels in a certain time.

  • The speed of light is measured in metres per second (m/s).
  • Light travels through a vacuum at 300,000 kilometres per second.
  • The exact speed at which light travels through a vacuum is 299,792,458 metres per second.
  • Light travels through other media at lower speeds.
  • A vacuum is a region of space that contains no matter.
  • Matter is anything that has mass and occupies space by having volume.
  • When discussing electromagnetic radiation the term medium (plural media) is used to refer to anything through which light propagates including empty space and any material that occupies space such as a solid, liquid or gas.
  • In other contexts empty space is not considered to be a medium because it does not contain matter.

https://en.wikipedia.org/wiki/Speed_of_light

Speed of light

The speed (or velocity) of a light wave is a measurement of how far it travels in a certain time.

  • The speed of light is measured in metres per second (m/s).
  • Light travels through a vacuum at 300,000 kilometres per second.
  • The exact speed at which light travels through a vacuum is 299,792,458 metres per second.
  • Light travels through other media at lower speeds.
  • A vacuum is a region of space that contains no matter.
  • Matter is anything that has mass and occupies space by having volume.
  • When discussing electromagnetic radiation the term medium (plural media) is used to refer to anything through which light propagates including empty space and any material that occupies space such as a solid, liquid or gas.
  • In other contexts empty space is not considered to be a medium because it does not contain matter.

Subtractive colour

A subtractive colour model combines different hues of a colourant such as a pigment, paint, ink, dye or powder to produce other colours.

  • CMYK is a subtractive colour model.
  • CMYK pigments are the standard for colour printing because they have a larger gamut than RGB pigments.
  • CMYK printing typically uses white paper which has good reflective properties and then adds cyan, magenta, yellow and black ink or toner to produce colour.
  • Highlights are produced by reducing the amount of coloured ink and printing without black to allow the maximum amount of light to reflect off the paper through the ink.
  • Mid tones rely on the brilliance and transparency of the pigments and the reflectivity of the paper to produce fully saturated colours.
  • Shadows are produced by adding black to both saturated or desaturated hues.

https://en.wikipedia.org/wiki/Subtractive_color

Sun

The Sun is the star at the centre of our solar system.

Here are some basic facts about the Sun:

https://en.wikipedia.org/wiki/Sun

Sunlight

Sunlight is light from the Sun and is also called daylight or visible light.

https://en.wikipedia.org/wiki/Sunlight

Sunlight

Sunlight is light emitted by the Sun and is also called daylight or visible light.