Parallax refers to how the appearance of an object can differ according to the place from which it is observed or the conditions of the observation. Different types of parallax are described briefly below.
1) Binocular parallax:The difference in the appearance of an object as seen by the right and left eyes. Binocular parallax makes depth perception possible.
2) Annual parallax:Changes that can be seen due to the revolution of the earth around the sun.
3) Diurnal parallax:Changes that can be seen due to the rotation of the earth.
4) Spectral parallax:Difference between the actual brightness of a star and its apparent brightness.
Binocular parallax arises from the difference in position that two objects of different distances are projected onto the retinas of the left and right eyes. One way to confirm this effect is the "random dot stereogram" experiment, in which what at first look appears to be an image of randomly distributed dots reveals a 3-D image when the eyes are focused properly.
