ABSTRACT
Sir Isaac Newton discovered that when a beam of light was passed through a solid wedge of glass it was broken up into a band of seven colours—red, orange, yellow, green, blue, violet and indigo. Newton also did the converse experiment of recombining the seven colours by means of a lens into white light again. We possess an instrument whereby we can tell whether all or some or none of the coloured rays in the light are coming from any given object; it is an arrangement of prisms known as the spectroscope. Although there are only seven colours in the spectrum, there are thousands of “colours” both in Nature and in the arts. Many colours not in the spectrum are formed by the mixing of two or more which are; and these mixed or compound colours may again be diluted with white or mixed with black.
