Far point: Difference between revisions

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== Optical Calculation ==
 
== Optical Calculation ==
Given the far point <math>FP</math> (in [[Metre|meters]]) of a person, the [[optical power]] of a [[convex lens]] (i.e. converging lens) necessary for them to see distant object clearly can be calculated as below:
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Given the far point <math>FP</math> (in [[Metre|meters]]) of a person, the [[optical power]] of a [[convex lens]] (i.e. converging lens) necessary for them to see distant object clearly can be calculated as below<ref>{{Cite web|url=https://courses.lumenlearning.com/physics/chapter/26-2-vision-correction/|title=Vision Correction {{!}} Physics|website=courses.lumenlearning.com|access-date=2019-12-05}}</ref>:
   
   

Revision as of 00:12, 5 December 2019

In visual perception, the far point is the point at which an object must be placed along the optical axis of the eye for its image to be focused on the retina when the eye is not accommodating. It is sometimes described as the farthest point from the eye at which images are clear.

For an unaccommodated emmetropic eye, the far point is at infinity, but for the sake of practicality, infinity is considered to be 6 m because the accommodation change from 6 m to infinity is negligible.

For an unaccommodated myopic eye, the far point is closer than 6 m. It depends upon the refractive error of the person's eye .

For an unaccommodated hypermetropic eye, incident light must be converged before entering the eye so as to focus on the retina. In this case (the hypermetropic eye) the focus point is behind the retina in virtual space, rather than on the retina screen.

Optical Calculation

Given the far point (in meters) of a person, the optical power of a convex lens (i.e. converging lens) necessary for them to see distant object clearly can be calculated as below[1]:

  1. ^ "Vision Correction | Physics". courses.lumenlearning.com. Retrieved 2019-12-05.