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Sir Isaac Newton, while studying the images of heavenly bodies formed by a lens, found that the images were coloured at the edges. In 1665, to investigate this, he performed an experiment using a prism. Newton darkened his room at Trinity College, Cambridge and allowed a beam of sunlight to pass through a small circular hole in the shutter forming a white circular patch on the opposite wall. He then placed a triangular prism in the path of the beam of light and observed that the white light was split into seven colours and that the seven colours resembled the colours of a rainbow namely violet, indigo, blue, green, yellow, orange and red (VIBGYOR).
This process of splitting of white light into its constituent colours when it is passed through a transparent medium is known as Dispersion.
The band of colours obtained due to the dispersion of white light is referred to as a spectrum.
From the above experiment Newton concluded that white light consists of a mixture of seven different colours.
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