Question

explain how our eyes can see the distant as well as nearly objects a s they are

Answer 1

Eyes can see distant as well as nearby objects just by adjusting focal length...

Eye muscles are relaxed when we see distant objects...at this stage our eye lens ( Convex lens) become thin and focal length is large...and Power of lens is a reciprocal of focal length...so for large focal length lens have less power...

When we see nearby object our eye muscles contracts as a results eye lens become thick...This decreses the focal length and increses the Power...

Here we see that just by adusting the focal length , Our eye accomodate Power as for larger focal length it increases less power and for small focal length it accomodate more power...This adjustment of focal length is called Power of accomodation...

Note that...in order to see the object clearly whether it is distant object or nearby...You should remember that The focus must be on the Object....

So if you want to see distant object...u need a large focal length so that eye can easily set the focus on same object that you want to see...In this situation eye lens become thin and relaxed and power of eye also become less...

Similarly in order to see the Nearby object...eye must set the focus on the nearby object..by doing so we need a short focal length...whcih increases power of the eye lens and cause Eye under Tension...