Color Spectrum Chart

Remember the science projects that we were so fond of making during school days? All the models made by the fellow students used to always leave me in awe. Nevertheless, one particularly interesting model that had caught my eye during that period, was the color wheel model. Not just me, many other students used to gape with admiration at the project during the demonstration. I am sure everyone of those wide-eyed students were keen to find the secret behind its technique. It was only after I walked into the physics class after years of watching those working wonders, that I actually learned the mystery behind its logic. The below given color spectrum chart will help you to understand the concept well.

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. Read more on properties of electromagnetic waves.

Brief Overview of the Color Spectrum Chart

THz - Terahertz.
nm - nanometer.

Color	Frequency (THz)	Wavelength(nm)
Violet	668-789	380-450
Blue	606-668	450-495
Green	526-606	495-570
Yellow	508-526	570-590
Orange	484-508	590-620
Red	400-484	620-750

The frequency of range of wavelength 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. In 1802, scientist Thomas Young was the first to calculate the wavelengths of different colors of light.