Imagine the whole world in black and white color? Or picture the main plot of the movie Pleasantville if you have seen this flick? Just a mental image of a stark world devoid of colors is enough to reveal the importance of colors in our lives. Whether you are feeling blue after a hard day's of work or going green with envy after seeing your neighbor's fancy TV, the colors have become a language through which we express ourselves. It's no wonder that the rainbow is often perceived as one of the most beautiful aspects of nature. Colors form when light falls on different objects and reflects as well as scatters different wavelengths. The scattered wavelengths are what see as colors.
Spectrum of Colors
Spectral colors are generally produced by monochromatic light i.e. visible light of a single wavelength. The spectrum appears continuous. Therefore, there are no definite boundaries between the colors. However, the approximate ranges of wavelength and frequency can be used to specify the difference. The most prominently apparent ones are violet, blue, green, yellow, orange and red. In reality, there are seven colors in the color spectrum with the addition of indigo between blue and violet. This was concluded by Newton after he successfully carried out experiments to disseminate a beam of monochromatic light by projecting it onto a glass prism at a specific angle to display the spectral colors. However, the frequency of the indigo color cannot be distinguished and recognized significantly by normal human eye, leaving the exception of some well-sighted people. Hence, it was suggested that indigo be dropped from the spectral chart and should be considered a shade of blue or violet.
From his experiments, Sir Isaac Newton observed that when a beam of monochromatic light falls on a prism, part of the light gets reflected whereas some part of it passes through the prism and a band of spectral colors emerges from it. From this, Newton speculated that light was made up of particles of different colors and that these particles move with different speeds in different media; their speed depending on the density of the medium. Red light was found to move faster than violet light in glass medium.
The visible spectrum or color spectrum is a subset of the electromagnetic spectrum. The electromagnetic spectrum is a range of frequencies of different energy waves such as gamma rays, X rays, ultraviolet rays, visible light, infrared waves, microwaves and radio waves. The visible light frequencies lie between the frequencies of the ultraviolet rays and infrared waves.
|Color||Frequency (THz)||Wavelength (nm)|
|❋ THz - terahertz|
|❋ nm - nanometer|
The frequency of wavelength range for indigo is around 425-450 nm and frequency of 670-700 THz. In the above color spectrum chart, indigo is made a subset of violet color. The low range of the color explains why it is difficult to distinguish this color in the spectral band. Since indigo is scientifically not recognized as a separate color, any wave having a wavelength of less than 450 nm is considered to be violet. Whereas gray, white and black are considered to be non-spectral colors. In fact, black is not even a color. Instead, it is the lack of color. Just as when there is light present (being the source of colors), it produces colors. Deficiency of light results in blackness. On the other hand, white is a mix of all the possible colors of the visible spectrum.
Although there are infinite number of color shades and hues, we all have a favorite one which somehow speaks to us more than others. Needless to say, these colors play an important role in our lives and affect our perception and behavior profoundly.