Mixing of Colours

• To introduce the basic elements of human perception of colours
• To study the composition of colours: additive and subtractive synthesis

The colour of the objects we see is largely due to the way those objects interact with light and ultimately reflect or transmit it to our eyes. The color of an object is not actually within the object itself. Rather, the color is in the light which shines upon it and is ultimately reflected or transmitted.

We know that the visible light spectrum consists of a range of frequencies, each of which corresponds to a specific color. When visible light strikes an object and a specific frequency becomes absorbed, that frequency of light will never make it to our eyes. Any visible light which strikes the object and becomes reflected or transmitted to our eyes will contribute to the color appearance of that object.

As we have seen in one of the experiences suggested in this manual, a prism can be used to break apart white light into its component colours. This shows that white light is a mixture of colours.

Although the spectrum shows that white light contains a continuous range of colours, colours from just three areas of the spectrum could be mixed to form any other colour including white. These three colours come from the red, green, and blue parts of the spectrum. We are now going to investigate the additive and subtractive colour synthesis.

Additive Colour Synthesis is the method of creating a colour by mixing various proportions of two or three distinct primary colours of light.

The most common example of additive colour synthesis is the colour television screen, (or RGB monitor), which is a mosaic of red, green, and blue phosphor dots; at normal viewing distances the eye does not distinguish the dots, but blends or adds their stimulus effects to obtain a composite colour effect.

The only role that the object plays is that it might contain atoms capable of selectively absorbing one or more frequencies of the visible light which shines upon it.

Subtractive Colour Synthesis uses paints, dyes, inks, and natural colorants to create colours by absorbing some wavelengths of light and reflecting or transmitting others. This subtractive action is the basis of photographic filters, almost all films and colour papers.

• Ray optics and colour mixing box with lamp, coloured filters and 2 side parts with mirror — 4402.30

• The light arriving on the Earth’s surface due to the emission of the sun is called ‘white light’. Do you think that white is a primary colour, a secondary one or a combination of more than two colours?