Color Spectrum Wavelength

Have you ever experimented looking through a prism and seen a continuous range of colors? Just like the rainbow in the sky. Have you ever pondered over this subject as to where do these different colors come from? Well these colors are called spectral colors (known as- the visible spectrum). Here is the answer to your question. These spectral colors that are seen through a prism or in a rainbow produced by visible light, are composed of a single frequency or wavelength (monochromatic light) which gives out pure spectral colors. A color spectrum or display of light or radiation are also known to be separated by wavelength, energy, frequency or some different properties. A visible light is a minuscule part of the electromagnetic spectrum.

What is Color Spectrum Wavelength

In olden days, it was known that color was a mixture of light and darkness and the prisms that were used colored the light. But today to define pure colors in conditions of the wavelengths of light, works out very well. All the colors that we perceive usually differs, depending upon the wavelength of the light that we see. The major reason of human eyes comprehending colors is because there are specific wavelengths of light that stimulates the retina of our eyes. This is why we see colors. The progression of the wavelength is from left to right, i.e. from long wavelength as red to short wavelength as violet or from low frequency light to high frequency. It is commonly expressed in terms of nanometers [1 nm = 10-9 m]. Here is a chart for you to understand the appropriate ranges. The wavelength of visible light spectrum is approximately from 750nm (red end) to 450nm (violet end) and the range of wavelengths that a human eye is able to perceive is termed as 'visible light'. Now although the spectrum is continuous, ranges are used as an approximation, with unclear boundaries between one single color and the next.

The Man Behind this Theory

Although earlier Roger Bacon had discovered the visible spectrum by experimenting it in a glass of water, the most former explanations of optical spectrum came from Sir Isaac Newton, from two of his theories; Opticks and Goethe-- Theory of Colors. The color circle of Newton's theory from Opticks, showed the correlation of the colors with the musical notes. All the spectral colors are arranged from red to violet separated by the notes of the musical scale. This circle helped to complete a full octave, which was from D to D. This circle diagram is a big hit to understand the basic of this theory. It passes from one end of the spectrum, i.e red next to the other end, i.e. violet, reflecting the concept that when violet and red lights are mixed, non-spectral purple colors are seen. Isaac Newton divided the color spectrum into seven different colors namely; red, orange, yellow, green, blue, indigo and violet, famously known as (VIBGYOR). This is the reason why, the wavelengths are different for each of these colors.

Demonstration of Color Spectrum Wavelength

This is a classroom demonstration of a color spectrum and here we would see the appearance of the colored objects in the colored light.

Apparatus and Material Required

1. High-dispersion prism (flint or lead glass)
2. Convex lens
3. Lens holder
4. Light source, compact
5. Power supply for light source, low voltage, variable
6. Two retort stands and bosses
7. Pieces of colored filter

Safety: Do not look directly at the bulb and try to treat the compact source of light with utmost care, as it is an effective source of UV. The lens to be used in the apparatus will ultimately filter out the UV.

Procedure

1. To produce an intense line of light, set the light source at one end of the laboratory.
2. About 3 m away, place the lens in way that produces a sharp image on the distant scree.
3. Now beyond the lens, keep the glass prism in the beam and rotate it to, so that the rays are swung round the prism.
4. Further, move the screen at any deviation to produce a suitable spectrum.
5. Through a selection of colored filters, take a look at the spectrum.
6. The impression of the primary and secondary colored filters on the white light spectrum should be marked.
7. For instance, take a look through a sheet of stamps by holding them in the different parts of the spectrum.

Some Technical Notes

• If the source is a line filament or compact parallel to the edge of the prism, no slit is required.
• It'll be beneficial to reduce the light level in the lab.
• If in case you do not have a (quartz iodine lamp)- source of light, use a 12 V lamp overrun to 14 or 16 V.

Newton's contemporaries amazed the moment he experimented a beam of sunlight with a glass prism. If you wish to carry out some similar experiment, do not complicate the optical system. You can try one of the Newton's smart way- experiments, by piercing a hole in the cardboard on which he had managed to catch the spectrum. Then try a second prism with a single color light, beaming through the hole and you will see no enhancement of a new range of colors. It gives a firm hint, that the colors are there in a mixture, just waiting to be sorted out completely. This is known to be the most sensible experiments by Isaac Newton.

Shorter wavelengths of visible light are known to be in the ultraviolet range (violet color) whereas, longer wavelengths are known to be in the infrared range (red color). It is impossible for a human eye to see any of these ranges, i.e., ultraviolet or infrared. Perhaps, we can perceive the wide range of colors, deeming on the weakness or strength of the different wavelengths in the colo. However, the white light is totally a mixture of the enormous visible spectrum and black on the contrary is the absence of light.