The need for two eyes
Binocular vision is when both eyes work together to draw information about an object. The advantage is the ability to perceive depth and gauge distances.
Appreciate the need for two eyes to increase the range and perceive objects in three dimensions.
Hold both arms in front of you about 30cms apart. Touch both first fingers together with both eyes open. Do this as often as you can in 10 trials. How many times did you succeed? Now shut your left eye. Repeat the trials as fast as you can. Repeat the experiment with your right eye shut. Are two eyes better than one?
Hold the bottom end of a pen at arms length. With both your eyes open, lower its cap on to it. How easy was it? Now close your left eye. Lower the cap on to the pen. Repeat it with your right eye closed and left eye open. Was it easier? What all can two eyes do better than one eye? Take care not to hurt yourself.
Get a partner to hold a pencil, point uppermost, at various distances in front of you. Keeping both eyes open try to touch the point of you partner's pencil with a pencil of your own. Try with right eye closed. Try with left eye closed. When was it easiest? Can you explain why?
On a white card, draw a circle the size of a 25 paise coin. Colour it up. Hold it in front of your face with one hand. Center your nose over the coloured circle. Focus your eyes on the circle. Put your free thumb in front of your nose. Continue to focus on the circle. What do you see? Now, switch your focus to your thumb. What do you see?
Roll up a tube of paper and look through it with your right eye. Place your open hand against the middle of the tube and look at it with the left eye. What do you see? Try closing one eye, left first and then the right. What do you see? What do you think is the reason for what you see?
Look at other animals, for example, cows or horses. How are their eyes placed on their heads? How is it advantageous for these animals to have their eyes placed as they are?