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The Basis of Color Substance

Colors captivate us all around us, but have you ever wondered what it is that imparts distinct colors to different materials, even if natural light is colorless? In fact, the colorless light we see is made up of many colors. When a colorless beam of light travels through a prism, it is resolved into its constituent colors, as you have all witnessed. The simple observation that white light is made up of many colors is the beginning point for finding a solution to the fundamental issue of what causes the color of materials.

The color of a substance is determined by both physical and chemical characteristics, which are addressed in this article.

We are going to discuss the physical characteristics:

Color Absorption

A transparent liquid or solid media transmits all of the component colors of white light without resolving them and appears colorless. A colored media is one that selectively absorbs some colors while reflecting or transmitting others. Complementary colors are those that are transmitted or reflected from one another. A complementary color wheel displays the color of a substance based on the absorption of wavelengths diagonally opposite the color of appearance on the wheel.

white light combination
white light composite of colors
color wheel
Color wheel complimentary
wavelengths of colors
Color wavelengths that make up white light

Pigments or dyes are highly absorbent compounds that absorb certain wavelengths. Polycrystalline powders or agglomerates of inorganic pigments are often dissolved in soluble oils. Organic pigments, on the other hand, are far more common in nature. The red color of hemoglobin and the green color of chlorophyll in plants and leaves are two examples.

Color Diffuse Reflectance

Coloured polymeric granules and sheets
Polymeric granules and sheets in various colors

Rough surfaces refract incident light in a variety of ways. Because the crystals of common salt reflect light rather than absorb it, it looks white. Copper sulfate crystals, on the other hand, look blue because they absorb higher wavelengths like red, yellow, and green and reflect blue wavelengths.

Scattering of Light

Particles in the path of light disperse it. The sky’s blue look is a famous example. The blue wavelengths of incoming sunlight are dispersed more forcefully by particles smaller than the wavelengths of light than the red wavelengths. Greater particles or pollutants in the atmosphere, with sizes on the order of light wavelengths or much larger, scatter light in the forward direction, and because scattering is not color dependent, clouds or pollution plumes look hazy white.

Color Chromophore 

Atoms or groupings of atoms organized in various molecular configurations make up all matter. Compound colors are caused by certain of these arrangements or functional groupings. Chromophores are the names given to such groupings. When bombarded with light, a chromophore is capable of electronic transitions in the UV–visible spectral range, imparting color to the molecule. ß-carotene, quinonones, porphyrins, and azo dyes are among examples.