Question

why the power of a lens depends upon its focal length???

Answer 1

because focal length decides how the image will form
if fol length is less then image formed is shorter
but when length is more more magnifide image has formed.
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Answer 2

Answer:

This is because, Focal length determines the distance of object as well as size of the object.

If Focal Length is said to be more, then we would have a greater focus due to which converging takes place from infinity.

Similarly the vice versa happens if the converging and focal length is small.

So the ability of changing focal length is called Power of accommodation or Power of eye.

Since it is dependent on Focal Length for Image formation, Power depends on Focal Length.

The relation between Power and Focal Length is :

Power ∝ 1 / Focal Length

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