The Human Eye and the Colourful WorldIntroduction
It is eye-check day at Riya's school. One by one, the students cover one eye and read the letters off a chart on the far wall. Aman, who sits on the last bench, squints at the third row and gives up. Riya reads all the way down to the tiny letters at the bottom. Same chart, same room, same light. So why can one pair of eyes read it when the other cannot?
Before we answer that, try something. Shut your eyes for a moment. You can still tell a lot about the world around you. Drag each thing into the right bucket: can you tell it with your eyes closed, or only with your eyes open?
Smell, sound, taste and touch tell you a great deal with your eyes shut, but colour is the one thing only your eyes can tell you. That makes the eye perhaps the most valuable of all our sense organs. In the last chapter you learnt how lenses refract light and form images. In this chapter you will see those same ideas at work inside your own eye, find out why some eyes need glasses and how the glasses fix them, and then turn to light in nature: how a glass prism splits white light into colours, how raindrops make a rainbow, why stars twinkle and why the clear sky is blue.