At different distances object is seen of different sizes but there is some distance at which actual size of object is seen through eyes. Is it 25cm?


1 Answer 1


The "size" of an object that you see is related to the angle subtended by the object at your eye.
The angle is called the visual angle.
This will determine the size of the image of the object on your retina.

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The closer the object is to your eye the bigger the image on your retina and so the bigger the object appears to be.

However there is a minimum distance that the object can be from your eye and with the object closer than the "least distance of distinct vision" the image on your retina is no longer in focus.
The position of the image at the least distance of distinct vision is called the near point.

As a a rule of thumb for the "average" eye the least distance of distinct vision is taken to be 25 cm and when an object is placed at that distance from the eye a focussed image has its maximum size.


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