WHY SOME COLOURS FADE WHEN EXPOSED TO THE SUN?

WHY SOME COLOURS FADE WHEN EXPOSED TO THE SUN?

PROF WAQAR HUSSAIN

           

               An object appears coloured on account of its reflecting certain waves of light to the eyes.   The power of reflecting light depends mostly on its structure and the nature of the molecules from which it is made. When the sun shines and pours light and heat, It causes certain changes in chemical state of bodies. Some of the changes affect the structure of the altered body in such a way that its surface 

reflects less light than it did before. This lesser reflection, in other words, means that its colour has faded.  When some artificial colours are exposed to the sun, their molecules undergo chemical changes and reflect lesser amount of waves of light. However, the colours of living flowers are strongly built and are not transformed easily. In case of dead plants sunlight fades their colour. Recently, some artificial colours are prepared that do not easily fade in sunlight.