Close your eyes and try to identify different objects by feeling them with your hand. Why is it possible for you to identify things like a note-book, text-book, bench, compass-box, etc. only by touching them?

Try this. i. Try to read a book keeping it very far from your eyes. ii. Try to read a book keeping it very close to your eyes. iii. Try to read a book keeping it at a distance of 25 cm from your eyes. At which time you see the alphabets clearly? Why?