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www.GOALias.blogspot.coma white sheet of paper or on a white wall.What do you observe? Do you see colourssimilar to those in a rainbow (Fig.15.30)? This shows that the sunlightconsists of seven colours. The sunlightis said to be white light. This means thatthe white light consists of seven colours.Try to identify these colours and writetheir names in your notebook.Can we mix these colours to get whitelight? Let us try.Activity 15.12Take a circular cardboard disc of about10 cm diameter. Divide this disc intoseven segments. Paint the sevenrainbow colours on these segmentsas shown in Fig. 15.31 (a). You canalso paste, coloured papers onthese segments. Make a small holeat the centre of the disc. Fix thedisc loosely on the tip of a refill of aball pen. Ensure that the disc rotatesfreely [Fig. 15.31 (a)]. Rotate the discin the daylight. When the disc isrotated fast, the colours get mixedtogether and the disc appearsto be whitish [Fig. 15.31 (b)]. Sucha disc is popularly known as Newton’sdisc.Fig. 15.31 (a) A disc with seven colours (b) It appears white on rotatingPaheli has a brilliant idea! Shehas prepared a small top witha small circular disc withseven rainbow colourspainted on it (Fig. 15.32).When the top rotates itappears nearly white.Fig. 15.32 A top with seven colours187LIGHT187