Red: Why Apple, Chili pepper, Blood, Ruby, Rose and Mars Red?
Very detailed explanation of Light and electromagnatic waves
Rainbow colors are described by the word "VIBGYOR" and 'R' in the word stands for RED. Red have the longest wavelength and lowest frequency among the visible light. That is the reason why we see sun red in the evening. light of shorter wavelength and higher frequency are scattered most in the atmosphere and in the evening when sun is near the horizon, light have to pass thicker atmosphere to reach us so almost all the blue and green light is scattered and red light reaches us.
Different wavelenghts and frequencies of light produce different colors: violet, indigo, blue, green, yellow, orange and red. when white light is fragmented you see seven distinct shades like in prism and rainbow. when all the shades are mixed up again they become white light.
From where so many colors come from?
Every molecule has electrons around it and these electrons are in different energy state, which means that every electron needs a particular wavelength as energy to move from current energy level to next energy level. No less than or more than the particular frequency will excite that electron to next level.
When a particular wavelength is absorbed by electrons from white light then resultant light would have a shade of remaining wavelengths. For example if blue light is absorbed from white light than resultant would be yellow light.
There are some special arrangement in many compounds which are responsible for color of the compound they are called chromophores
Bright red color of our blood is due to the presence of hemoglobin in the blood, hemoglobin is a complex quaternary protein in our blood cells each protein complex consist of four heme group and each heme group inhabit one ion of iron Fe3+. when this ion is bonded with oxygen it gives out bright red color. Therefore capillary and arterial blood is very bright red and on other hand venous blood which we see in blood donation is darker shade of red because it is deoxygenated.
This shows that iron in our blood is responsible for its color, and oxygen bonding with iron enhance its brightness. On an average adult human body have 5.2 litres of blood and amazingly only one gram iron is sufficient for all blood's hemoglobin. this means that color of blood is only due to 0.019 percent of its own matter.
Ruby is the crystal of mineral corundum,generally crystal of corundum is colorless but some minute impurities give this crystal bright colors. Ruby is aluminum oxide crystal with impurity of chromium, aluminium3+ ions are replaced by chromium3+. but amazing fact is that less than one percent of this replacement is sufficient to give bright red color, and up till 1% replacement will give dark shade of red . ruby
Amazing fact is that red color of different chillies is not at all related to their hotness, in fact Pure capsaicin which is responsible for chilli's hot sensation is colorless, odorless and waxy substance. The red hot color of chilli is actually from the organic pigment known as carotenoid and more particularly β-Carotene. This substance is also responsible for Carrot's orange-red color and many other yellow to red colored vegetables.
Anthocyanidins are a group of compounds which are present in plant tissues giving them color ranging from orange to blue-red color. is member of this family and it is present in apple skin giving it red color. this substance is also responsible for red color of grapes, cherry, cranberry, acai berry raspberry, plums, and red cabbage and red onion. Cyanidin
Roses and Peonies
Roses are another example for which anthocyanins are responsible for their red color. their are more than 300 types of anthocyanins in the family and every shade of rose have a unique combination of different anthocyanins.Peonin and Pelargonidin are two main family members which contribute to red color of roses.
Presence of anti-oxidant lycopene in tomato makes it red. lycopene is a type of carotenoid and is also present in carrot and watermelons and other vegetables and fruits.
The red color or mars is due to ferric oxide in the soil of mars, it is in the same way as heme group gives red color to the blood and the rust. Each iron oxide consists of two atoms of iron and three of oxygen.