Question

What is dispersion of white light? Is it possible to recombine the lights of seven colours to obtain the white light again? [3 marks]

Answer 1

• Dispersion is the splitting up of white light into seven colours on passing through a transparent medium like a glass prism. [0.5 marks]
• When a white light beam is passed through a prism, a band of seven colours are formed which is known as a spectrum of white light. The seven colours in the spectrum are red, orange, yellow, green, blue, indigo and violet respectively. [0.5 marks]
• If one more prism is arranged in opposite manner, then the dispersed colours will merge into white light beam again. All the colours will be arranged as violet, indigo, blue, green, yellow, orange and red from down to up. When these passes from the second prism, all join together and gives a white light as shown in the figure. [2 marks]