Limit of resolution: Two movable pin-points of light.

Limit of Resolution: Two small lamps on adjustable slide. Two lamps are mounted on a slide bar so that the spacing between the filaments is variable from 3 to 22 mm. (In addition, the intensity of each filament is individually variable.) The demonstration is pointed at the class and students at different distances from the lamps will experience different limits of resolution dependent upon the conditions set up by the instructor. The resolution of the human eye is limited by several factors. The resolution is best at the fovea, where cone spacing is the closest. Spherical and chromatic abberation degrade resolution. For an average pupil of about .9 cm, and at lambda = 550 nm the eye can resolve objects whose angular separation is about .0005 rad. Thus, at a distance of about 20 m, the eye can resolve the two point lamps at about 1 cm separation.