We are surrounded by colours …you name it… everything has a colour of some sort. As we stroll through our life, often we take for granted the dazzling range of colours in the world.
How many of us, looking at the tapestry of colour of a forest, lets say in October, ask the question, what makes colour what it is?
So, let’s answer that question; the colour that we see depends on few factors and the first one is visible light. It is the reason we are able to see anything; without it, we would be in complete darkness. So, what is visible light? It is the very narrow band of the electromagnetic radiation spectrum that our eyes are sensitive to; it consist of a range of frequencies, each of which corresponds to a specific colour (rainbow colours, ROYGBIV).
The colour of an object is not contained within the object. Objects appear in different colours because they absorb some wavelengths and reflect or transmit other wavelengths from within the visible spectrum, e.g. in general we are seeing an object as red, when that object absorbs all frequencies and reflects just red frequency of the visible light.
White objects appear white because they reflect all colours. Black objects absorb all colours, so no light is reflected all the energy is stored as heat. That is why; in summer white shirts are better than black shirts to keep you cool.
For an object to be transparent (like glass or water) it must allow light of one or more frequencies to be transmitted through the material without being reflected.
The role that the object plays in the perception of colour process is that it might contain atoms capable of selectively absorbing one or more frequencies of the visible light that shine upon it. Essentially everything is made up of atoms and these atoms and their electrons govern how something will look under light. This is where chemistry kicks in. The perceived colour of objects is the result of interactions between the various frequencies of visible light waves and the atoms that objects are made of.
The sky on a sunny day is blue because the molecules of air scatter blue light more than the red light. At sunset, the angle of the light changes and we see red and orange because the blue light has been scattered out and away from the line of sight leaving just the reds.
Oceans are blue because red, orange and yellow wavelengths are absorbed more strongly by water molecules than the blue, so when white light from the sun enters the ocean, blue is the wavelength that is reflected.
Now, there are also some chemicals that contain atoms capable of either selectively absorbing, reflecting or transmitting one or more frequencies of light, known as pigments. The deep green colour of leaves in summer is due to a natural pigment known as chlorophyll which absorbs red and blue wavelengths. As leaves lose their chlorophyll, other pigments (carotenoids with the range in colour from yellow to red) become visible and the colour of leaves turns vivid yellow and orange. When leaves turn brown, it is an indication that all the pigments are gone.
After all this, I think, that the best definition of colours was given by Johann Wolfgang von Goethe’s in his work “Theory of Colours” where he says “colours are light’s suffering and joy”.
–Dana Plesa
