What is human eye

 Human eye

It is called natures photographic camera.A human eye has certain limit of magnifying power.it can not view details of an object below near point and beyond far point.Therefore optical instrument like microscope, Telescope,are made up of optical elements like spherical mirror,lenses which assist human eye in viewing detales of an object.

Near point

The nearest object

position whose image can be focussed on the retina.

Least distance of distinct vision

The distance of near point from eye is called Least distance of distinct vision or comfortable distance for viewing image. 

The average distance for clear vision is 25cm.

Far point

The farthest object position whose image can be focussed on the retina.

Range of vision

 The distance between near point and far point is called range of vision.for normal eye it is 25cm to infitive.

Accommodation power

The power of eye lense to focus the image of object (near or far) on the retina is called accommodation power.