Primary Colors, Secondary colors and Complimentary Colors

When a beam of white light is passed through a prism, white light splits up into different colours. Consequently a coloured pattern is obtained on the screen.

This splitting of white light into its constituent colours is called dispersion of light. The coloured patent obtained on the screen is called a spectrum. The colours are not in strips but change gradually through many different shades of colour. The colours of the spectrum of white light are violet, indigo, blue, green, yellow, orange and red (VIBGYOR). The white light is a mixture of different colours. Each colour is associated with light of a particular wavelength. Red light has longer wavelengths than the blue light. The angle of deviation by a prism is not the same for all the wavelength (colours) of light. Hence the prism disperses white light into its constituent colours. The red is deviated least and the violet most.

Color of Objects

The colour of an object depends upon the colour of light it reflects. If all colours are reflected the object appears white. If some colours are reflected, the object appears coloured. The colour seen by the eye is the colour of the reflected light. A ball appears red when it is seen through a piece of red glass. White objects reflect all colour and black objects absorb all colours. Red objects reflect red only and absorb other colours.

Primary Colors, Secondary colors and Complimentary Colors

Primary colours are sets of colours that can be combined to make a useful range of colours. For human applications, three primary colours are usually used, since human colour vision is trichromatic. For additive combination of colours, as in overlapping projected lights or in CRT displays, the primary colours normally used are red, green, and blue. For subtractive combination of colours, as in mixing of pigments or dyes, such as in printing, the primaries normally used are cyan, magenta, and yellow, though the set of red, yellow, blue is popular among artists.  The colours obtained by mixing of any two primary colours are called secondary colours. Two colors are called complementary if, when mixed in the proper proportion, they produce a neutral color (grey, white, or black). The common complimentary colors are:

• red + green + blue
• yellow + blue
• magenta + green
• cyan + red