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Question
How could you show that the colours of the spectrum combine to give white light?
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Solution
We know that a spectrum of colours is formed when a beam of white light is passed through a transparent glass prism. These colours can be recombined to give white light again. This is achieved by placing another glass prism upside down behind the first prism. A patch of white light is obtained on a screen placed behind the second prism because the refraction produced by the second prism is equal and opposite to the refraction produced by the first prism.
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Make a rainbow
Try to make your own rainbow. You can try this project in the morning or in the evening. Stand with your back towards the Sun. Take a hosepipe or a water pipe used in the garden. Make a fine spray in front of you. You can see different colours of rainbow in the spray.
