The colourful world

  Imagine a world without colours-no green leaves,no blue sky, no rainbow,no paint,no crayons.

 Colours add emotions to life and without them,everything becomes very dull and uneventful.i am sure that old movies will be a lot better if released in colour. The colour of an object is a very complex result of its surface characteristics, transmission properties, emission and absorption properties. It is further influenced by the ambient illumination and the colour properties of objects nearby(i.e. colour constancy).

Let us take a look at factors that the colour of an object depend on:

Light arriving at an opaque surface is either reflected "specularly" (that is, in the manner of a mirror), scattered (that is, reflected with diffuse scattering), or absorbed – or some combination of these.

Opaque objects that do not reflect specularly (which tend to have rough surfaces) have their color determined by which wavelengths of light they scatter more and which they scatter less (with the light that is not scattered being absorbed). If objects scatter all wavelengths, they appear white. If they absorb all wavelengths, they appear black.

Opaque objects that specularly reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences. An object that reflects some fraction of impinging light and absorbs the rest may look black but also be faintly reflective; examples are black objects coated with layers of enamel or lacquer.

Objects that transmit light are either translucent (scattering the transmitted light) or transparent (not scattering the transmitted light). If they also absorb (or reflect) light of various wavelengths differentially, they appear tinted with a color determined by the nature of that absorption (or that reflectance).

Objects may emit light that they generate themselves, rather than merely reflecting or transmitting light. They may do so because of their elevated temperature (they are then said to be incandescent), as a result of certain chemical reactions (a phenomenon called chemoluminescence), or for other reasons (see the articles Phosphorescence and List of light sources).

Objects may absorb light and then as a consequence emit light that has different properties. They are then called fluorescent (if light is emitted only while light is absorbed) or phosphorescent (if light is emitted even after light ceases to be absorbed; this term is also sometimes loosely applied to light emitted because of chemical reactions).:

When the reflected light has a wavelegth that comes under the visible light's wavelength (390nm to 750nm),then we are able to see the colour of the light.

Colours and the Eye:

  The ability of the human eye to distinguish colors is based upon the varying sensitivity of different cells in the retina to light of different wavelengths. Humans being trichromatic, the retina contains three types of color receptor cells, or cones. One type, relatively distinct from the other two, is most responsive to light that we perceive as violet, with wavelengths around 420 nm; cones of this type are sometimes called short-wavelength cones, S cones, or blue cones. The other two types are closely related genetically and chemically. One of them, sometimes called long-wavelength cones, L cones, or red cones, is most sensitive to light we perceive as greenish yellow, with wavelengths around 564 nm; the other type, known as middle-wavelength cones, M cones, or green cones is most sensitive to light perceived as green, with wavelengths around 534 nm.

Colours and the Brain:
  While the mechanisms of color vision at the level of the retina are well-described in terms of tristimulus values (see above), color processing after that point is organized differently. A dominant theory of color vision proposes that color information is transmitted out of the eye by three opponent processes, or opponent channels, each constructed from the raw output of the cones: a red–green channel, a blue–yellow channel, and a black–white "luminance" channel. This theory has been supported by neurobiology, and accounts for the structure of our subjective color experience. Specifically, it explains why we cannot perceive a "reddish green" or "yellowish blue", and it predicts the color wheel: it is the collection of colors for which at least one of the two color channels measures a value at one of its extremes.
     People who are colour blind have a defect in their cones,i.e, if they are less responsive than a normal cone or if one or more of the cones are missing and these people will not be able to effectively distinguish between the different colours. It is incredible to know that while human beings a trichromatic, spiders, birds and reptiles are tetrachromatic, which means that their eys percieve light in a more characterised manner. There are more such interesting facts about colours and the way living beings percieve them,for example, synesthesia.

    Eye-opening? haha. I feel blessed to have an organ that lets me enjoy the beauty of the world. This compels me to make a suggestion. Donating our eyes should be made mandatory. This will make someone else's life better.