Yellow is the color between green and
orange on the spectrum of visible light. It is evoked by light with a dominant
wavelength of roughly 570–590 nm. It is a primary color in subtractive color
systems, used in painting or color printing. In the RGB color model, used to
create colors on television and computer screens, yellow is a secondary color
made by combining red and green at equal intensity. Carotenoids give the
characteristic yellow color to autumn leaves, corn, canaries, daffodils, and
lemons, as well as egg yolks, buttercups, and bananas. They absorb light energy
and protect plants from photodamage. Sunlight has a slight yellowish hue, due
to the surface temperature of the sun.
Because it was widely available, yellow
ochre pigment was one of the first colors used in art; the Lascaux cave in France Europe were forced to wear a
yellow star. In China
According to surveys in Europe, Canada , and the United
States , yellow is the color people most often associate
with amusement, gentleness, humor, and spontaneity, but also with duplicity,
envy, jealousy, avarice, and, in the U.S. Iran China
Etymology
The word yellow comes from the Old English
geolu, geolwe (oblique case), meaning "yellow, yellowish", derived
from the Proto-Germanic word gelwaz "yellow". It has the same
Indo-European base, gʰel-, as the words gold and yell; gʰel- means both bright
and gleaming, and to cry out.
The English term is related to other
Germanic words for yellow, namely Scots yella, East Frisian jeel, West Frisian
giel, Dutch geel, German gelb, and Swedish and Norwegian gul. According to the
Oxford English Dictionary, the oldest known use of this word in English is from
The Epinal Glossary in 700.
Science and nature
Optics, color printing, and computer
screens
Yellow is found between green and orange on
the spectrum of visible light. It is the color the human eye sees when it looks
at light with a dominant wavelength between 570 and 590 nanometers.
In color printing, yellow is one of the
three colors of ink, along with magenta and cyan, which, along with black, can
be overlaid in the right combination, along with black, to print any full color
image. (See the CMYK color model). A particular yellow is used, called Process
yellow (also known as "pigment yellow", "printer's yellow",
and "canary yellow") subtractive primary colors, along with magenta
and cyan. Process yellow is not an RGB color, and there is no fixed conversion
from CMYK primaries to RGB. Different formulations are used for printer's ink,
so there can be variations in the printed color that is pure yellow ink.
The yellow on a color television or computer
screen is created in a completely different way; by combining green and red
light at the right level of intensity. (See RGB color model).
Complementary colors
Traditionally, the complementary color of
yellow is purple; the two colors are opposite each other on the color wheel
long used by painters. Vincent Van Gogh, an avid student of color theory, used
combinations of yellow and purple in several of his paintings for the maximum
contrast and harmony.
Hunt defines that "two colors are
complementary when it is possible to reproduce the tristimulus values of a
specified achromatic stimulus by an additive mixture of these two
stimuli." That is, when two colored lights can be mixed to match a
specified white (achromatic, non-colored) light, the colors of those two lights
are complementary. This definition, however, does not constrain what version of
white will be specified. In the nineteenth century, the scientists Grassmann
and Helmholtz did experiments in which they concluded that finding a good
complement for spectral yellow was difficult, but that the result was indigo,
that is, a wavelength that today's color scientists would call violet or
purple. Helmholtz says "Yellow and indigo blue" are complements.
Grassmann reconstructs Newton
Because of the characteristics of paint
pigments and use of different color wheels, painters traditionally regard the
complement of yellow as the color indigo or blue-violet.
Lasers
Lasers emitting in the yellow part of the
spectrum are less common and more expensive than most other colors. In
commercial products diode pumped solid state (DPSS) technology is employed to
create the yellow light. An infrared laser diode at 808 nm is used to pump a
crystal of neodymium-doped yttrium vanadium oxide (Nd:YVO4) or neodymium-doped
yttrium aluminium garnet (Nd:YAG) and induces it to emit at two frequencies
(281.76 THz and 223.39 THz: 1064 nm and 1342 nm wavelengths) simultaneously.
This deeper infrared light is then passed through another crystal containing
potassium, titanium and phosphorus (KTP), whose non-linear properties generate
light at a frequency that is the sum of the two incident beams (505.15 THz); in
this case corresponding to the wavelength of 593.5 nm ("yellow").
This wavelength is also available, though even more rarely, from a helium–neon
laser. However, this not a true yellow, as it exceeds 590 nm. A variant of this
same DPSS technology using slightly different starting frequencies was made
available in 2010, producing a wavelength of 589 nm, which is considered a true
yellow color. The use of yellow lasers at 589 nm and 594 nm have recently
become more widespread thanks to the field of optogenetics.
Astronomy
Stars of spectral classes F and G, such as
our Sun, have color temperatures that make them look "yellowish". The
first astronomer to classify stars according to their color was F. G. W. Struve
in 1827. One of his classifications was flavae, or yellow, and this roughly
corresponded to stars in the modern spectral range F5 to K0. The Strömgren
photometric system for stellar classification includes a 'y' or yellow filter
that is centered at a wavelength of 550 nm and has a bandwidth of 20–30 nm.
Biology
Autumn leaves, yellow flowers, bananas,
oranges and other yellow fruits all contain carotenoids, yellow and red organic
pigments that are found in the chloroplasts and chromoplasts of plants and some
other photosynthetic organisms like algae, some bacteria and some fungi. They
serve two key roles in plants and algae: they absorb light energy for use in
photosynthesis, and they protect the green chlorophyll from photodamage.
In late summer, as daylight hours shorten
and temperatures cool, the veins that carry fluids into and out of the leaf are
gradually closed off. The water and mineral intake into the leaf is reduced,
slowly at first, and then more rapidly. It is during this time that the
chlorophyll begins to decrease. As the chlorophyll diminishes, the yellow and
red carotenoids become more and more visible, creating the classic autumn leaf
color.
Carotenoids are common in many living
things; they give the characteristic color to carrots, corn, daffodils,
rutabagas, buttercups and bananas. They are responsible for the red of cooked
lobsters, the pink of flamingoes and salmon and the yellow of canaries and egg
yolks.
Xanthophylls are the most common yellow
pigments that form one of two major divisions of the carotenoid group. The name
is from Greek xanthos (ξανθος, "yellow") + phyllon (φύλλον,
"leaf"). Xanthophylls are most commonly found in the leaves of green
plants, but they also find their way into animals through the food they eat.
For example, the yellow color of chicken egg yolks, fat, and skin comes from
the feed the chickens consume. Chicken farmers understand this, and often add
xanthophylls, usually lutein, to make the egg yolks more yellow.
Bananas are green when they are picked
because of the chlorophyll their skin contains. Once picked, they begin to
ripen; hormones in the bananas convert amino acids into ethylene gas, which
stimulates the production of several enzymes. These enzymes start to change the
color, texture and flavor of the banana. The green chlorophyll supply is
stopped and the yellow color of the carotenoids replaces it; eventually, as the
enzymes continue their work, the cell walls break down and the bananas turn
brown.
Fish
Yellowtail is the common name for dozens of
different fish species that have yellow tails or a yellow body.
Yellowfin tuna (Thunnus albacares) is a
species of tuna, having bright yellow anal and second dorsal fins. Found in
tropical and subtropical seas and weighing up to 200 kg (440 lb), it is caught
as a replacement for depleted stocks of bluefin tuna.
Insects
The yellow-fever mosquito (Aedes aegypti)
is a mosquito so named because it transmits dengue fever and yellow fever, the
mosquito-borne viruses.
Yellowjackets are black-and-yellow wasps of
the genus Vespula or Dolichovespula (though some can be black-and-white, the
most notable of these being the bald-faced hornet, Dolichovespula maculata).
They can be identified by their distinctive black-and-yellow color, small size
(slightly larger than a bee), and entirely black antennae.
Trees
Populus tremuloides is a deciduous tree
native to cooler areas of North America , one
of several species referred to by the common name aspen. Populus tremuloides is
the most widely distributed tree in North America, being found from Canada to central Mexico
The yellow birch (Betula alleghaniensis) is
a birch species native to eastern North America, from Nova
Scotia , New Brunswick , and
southern Quebec west to Minnesota ,
and south in the Appalachian Mountains to northern Georgia
The thorny yellowwood is an Australian
rainforest tree which has deep yellow wood.
Yellow poplar is a common name for
Liriodendron, the tuliptree. The common name is inaccurate as this genus is not
related to poplars.
The Handroanthus albus is a tree with
yellow flowers native to the Cerrado of Brazil.
Fruits, vegetables, and eggs
Many fruits are yellow when ripe, such as
lemons and bananas, their color derived from carotenoid pigments. Egg yolks
gain their color from xanthophylls, also a type of carotenoid pigment.
Flowers
Yellow is a common color of flowers.
Other plants
Rapeseed (Brassica napus), also known as
rape or oilseed rape, is a bright yellow flowering member of the family
Brassicaceae (mustard or cabbage family).
Goldenrod is a yellow flowering plant in
the family Asteraceae.
Minerals and chemistry
Yellowcake (also known as urania and uranic
oxide) is concentrated uranium oxide, obtained through the milling of uranium
ore. Yellowcake is used in the preparation of fuel for nuclear reactors and in
uranium enrichment, one of the essential steps for creating nuclear weapons.
Titan yellow (also known as clayton
yellow), chemical formula C28H19Na2O6S4 has been used to determine magnesium in
serum and urine, but the method is prone to interference, making the ammonium
phosphate method superior when analysing blood cells, food or fecal material.
Methyl yellow (p-Dimethylaminoazobenzene)
is a pH indicator used to determine acidity. It changes from yellow at pH=4.0
to red at pH=2.9.
Yellow fireworks are produced by adding
sodium compounds to the firework mixture. Sodium has a strong emission at 589.3
nm (D-line), a very slightly orange-tinted yellow.
Amongst the elements, sulfur and gold are
most obviously yellow. Phosphorus, arsenic and antimony have allotropes which
are yellow or whitish-yellow; fluorine and chlorine are pale yellowish gases.
Pigments
Yellow ochre (also known as Mars yellow,
Pigment yellow 42, 43), hydrated ferric oxide (Fe2O3.H2O), is a naturally
occurring pigment found in clays in many parts of the world. It is non-toxic
and has been used in painting since prehistoric times.
Indian yellow is a transparent, fluorescent
pigment used in oil paintings and watercolors. Originally magnesium euxanthate,
it was claimed to have been produced from the urine of Indian cows fed only on
mango leaves. It has now been replaced by synthetic Indian yellow hue.
Naples Yellow (lead antimonate yellow) is
one of the oldest synthetic pigments, derived from the mineral bindheimite and
used extensively up to the 20th century. It is toxic and nowadays is replaced
in paint by a mixture of modern pigments.
Cadmium Yellow (cadmium sulfide, CdS) has
been used in artists' paints since the mid-19th century. Because of its
toxicity, it may nowadays be replaced by azo pigments.
Chrome Yellow (lead chromate, PbCrO4),
derived from the mineral crocoite, was used by artists in the earlier part of
the 19th century, but has been largely replaced by other yellow pigments
because of the toxicity of lead.
Zinc yellow or zinc chromate is a synthetic
pigment made in the 19th century, and used by the painter Georges Seurat in his
pointilist paintings. He did not know that it was highly unstable, and would
quickly turn brown.
Titanium Yellow (nickel antimony titanium
yellow rutile, NiO.Sb2O5.20TiO2) is created by adding small amounts of the
oxides of nickel and antimony to titanium dioxide and heating. It is used to
produce yellow paints with good white coverage and has the LBNL paint code
"Y10".
Gamboge is an orange-brown resin, derived
from trees of the genus Garcinia, which becomes yellow when powdered. It was
used as a watercolor pigment in the far east from the 8th century – the name
"gamboge" is derived from "Cambodia "
– and has been used in Europe since the 17th
century.
Orpiment, also called King's Yellow or
Chinese Yellow is arsenic trisulfide (As2S3) and was used as a paint pigment
until the 19th century when, because of its high toxicity and reaction with
lead-based pigments, it was generally replaced by Cadmium Yellow.
azo dye-based pigment (a brightly colored
transparent or semitransparent dye with a white pigment) is used as the
colorant in most modern paints requiring either a highly saturated yellow or
simplicity of color mixing. The most common is the monoazo arylide yellow
family, first marketed as Hansa Yellow.
Dyes
Curcuma longa, also known as turmeric, is a
plant grown in India and Southeast Asia which serves as a dye for clothing,
especially monks' robes; as a spice for curry and other dishes; and as a
popular medicine. It is also used as a food coloring for mustard and other
products.
Saffron, like turmeric, is one of the rare
dyes that is also a spice and food colorant. It is made from the dried red
stigma of the crocus sativus flower. It must be picked by hand and it takes 150
flowers to obtain a single gram of stigma, so it is extremely expensive. It
probably originated in the Mediterranean or Southwest Asia ,
and its use was detailed in a 7th-century BC Assyrian botanical reference
compiled under Ashurbanipal. It was known in India at the time of the Buddha,
and after his death his followers decreed that monks should wear robes the
color of saffron. Saffron was used to dye the robes of the senior Buddhist monks,
while ordinary monks wore robes dyed with Gamboge or Curcuma longa, also known
as Turmeric.
The color of saffron comes from crocin, a
red variety of carotenoid natural pigment. The color of the dyed fabric varies
from deep red to orange to yellow, depending upon the type of saffron and the
process. Most saffron today comes from Iran ,
but it is also grown commercially in Spain ,
Italy and Kashmir in India , and as a boutique crop in New Zealand , the United
Kingdom , France ,
Switzerland United
States
Reseda luteola, also known as dyers weed,
yellow weed or weld, has been used as a yellow dye from neolithic times. It
grew wild along the roads and walls of Europe, and was introduced into North America , where it grows as a weed. It was used as
both as a yellow dye, whose color was deep and lasting, and to dye fabric
green, first by dyeing it blue with indigo, then dyeing it with reseda luteola
to turn it a rich, solid and lasting green. It was the most common yellow dye in
Europe from the Middle Ages until the 18th century, when it was replaced first
by the bark of the quercitron tree from North America ,
then by synthetic dyes. It was also widely used in North Africa and in the Ottoman Empire .
Gamboge is a deep saffron to mustard yellow
pigment and dye. In Asia , it is frequently
used to dye Buddhist monks' robes. Gamboge is most often extracted by tapping
resin from various species of evergreen trees of the family Guttiferae, which
grow in Cambodia , Thailand , and elsewhere in Southeast
Asia . "Kambuj" (Sanskrit: कंबुज) is the ancient
Sanskrit name for Cambodia.
Food coloring
The most common yellow food coloring in use
today is called Tartrazine. It is a synthetic lemon yellow azo dye. It is also
known as E number E102, C.I. 19140, FD&C yellow 5, acid yellow 23, food yellow
4. It is the yellow most frequently used such processed food products as corn
and potato chips, breakfast cereals such as corn flakes, candies, popcorn,
mustard, jams and jellies, gelatin, soft drinks (notably Mountain Dew), energy
and sports drinks, and pastries. It is also widely used in liquid and bar soap,
shampoo, cosmetics and medicines. Sometimes it is mixed with blue dyes to color
processed products green.
It is typically labelled on food packages
as "color", "tartrazine", or "E102". In the United States
Another popular synthetic yellow coloring
is Sunset Yellow FCF (also known as 'orange yellow S, FD&C yellow 6 and
C.I. 15985) It is manufactured from aromatic hydrocarbons from petroleum. When
added to foods sold in Europe , it is denoted
by E number E110.
Source From Wikipedia
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