Pavni's mother had just washed all the white clothes. She was telling her friend that the whiteness of white clothes was decreasing with every wash and even new white clothes appeared to be like old ones after a few washings. Pavni, who is a student of class 10, was listening to her mother's complaint. Pavni then went to the market and purchased a particular 'dye'. She asked her mother to dissolve a little of this dye in a bucketful of water and soak the washed white clothes in the solution of dye for some time. Pavni's mother did the same. After sometime, the clothes were taken out of the bucket, rinsed well and spread on clothes line for drying. Pavni's mothers observed that the whiteness of washed white clothes had increased a lot after applying a little of the dye. Pavni's mother did not know why on applying little of a certain dye to washed white clothes, their whiteness had increased manifolds. Pavni explained everything to her mother.
(a) What could be the 'dye' applied by Pavni's mother to the washed white clothes by dissolving in water ?
(b) What does the application of this dye make the washed white clothes look even more white (or shining white) ? Explain.
(c) What values are displayed by Pavni in this episode ?

Explanation

(a) The dye applied by Pavni's mother to the washed white clothes is 'blue' ('blue colour' or 'neel').
(b) The white sunlight is a mixture of seven coloured lights, violet, indigo, blue, green, yellow, orange and red (which is called spectrum). Now, when the white sunlight consisting of seven different colours comes down through the atmosphere, then some of its blue colour is scattered by air molecules present in the atmosphere (causing the blue colour of the sky). In this way, the white sunlight becomes somewhat deficient in blue colour. When this sunlight (having deficiency of blue colour) falls on washed white clothes to which 'blue colour' (or neel) has been applied, then the deficiency of blue colour in white sunlight is made up. The white sunlight reflected from the washed white clothes now has all the colours of the spectrum in the right proportions and this makes the white clothes appear extremely white.
(c) Pavni displayed the values of (i) Knowledge of scientific facts (such as composition of sunlight, spectrum and scattering of light) (ii) Application of knowledge in real life situations (such as to make washed white clothes look more white), and (iii) Desire to help mother by solving her problem.