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www.GOALias.blogspot.comFig. 15.29 A CD placed in sunFig. 15.28 A rainbowseen as a large arc in the sky with manycolours (Fig. 15.28).How many colours are present in arainbow? When observed carefully, thereare seven colours in a rainbow, thoughit may not be easy to distinguish all ofthem. These are — red, orange, yellow,green, blue, indigo and violet.Does this mean that thewhite light consists ofseven colours?You might have seen that when youblow soap bubbles, they appearcolourful. Similarly, when light isreflected from the surface of aCompact Disk (CD), you see manycolours (Fig. 15.29).On the basis of these experiences,could we say that the sunlight is amixture of different colours? Let usinvestigate.Activity 15.11Take a glass prism. Allow a narrow beamof sunlight through a small hole in thewindow of a dark room to fall on oneface of the prism. Let the light comingout of the other face of the prism fall onPaheli wants to tell youthat you can see arainbow only when yourback is towards the sun.Fig. 15.30 A prism splits sunlight into seven colours186SCIENCE