Parallel wire problem and the mosquito net problem:

            Let me explain the problems one by one.

1.      Parallel wire problem: You must have seen parallel electric wires running between electric poles in front of our houses. These are multi strand twisted wires, which is what we want for our experiment. We have learnt that our brain perceives depth by correlating the left and the right images. This needs some uniqueness in the image for each point and the surface as a whole for the stereo correspondence to be unique. Now let me give you the picture of the set up I am looking for in this experiment. The two parallel wires have a separation of say one foot to start with and the nearest one is five foot from you. They lie on the same horizontal plane. Focus on the nearest one. Your eyes would have combined the images properly to give you a single image, but since the twisting of the wire strands are similar all along the length of the wire, doesn’t your eye make any mistake corresponding the two images? If the depth of the second wire is adjusted such that even the correspond exactly when the first wire is focused, your brain is fooled! It fails to perceive the depth between the two wires. It even works without any depth adjustment of the second wire; still I wanted to be on the safer side.

2.      Mosquito net problem: Here instead of a long twisted wire we have a netted structure. Try observing the net from a close distance such that your eye is just able to focus it. The net pops up and you feel as though it is some 5cm from you. You go to touch it but your hand just passes through the net and you will find it at a different depth.