In This post you will get answer of Q.
The power of a lens, a short sighted person uses is -2 D. Find the maximum distance of an object which he can see without spectacles:
Solution:
Image is formed at focus. We know that Power
$ (P)=frac{text{1}}{text{focal},text{length},text{(m)}} $ Given $ P=-2D $
$ therefore $ $ text{Focal},text{length},=-frac{1}{2}=-0.5,m $
$ Rightarrow $ $ F=-50,cm $
Hence, maximum distance of an object, which he can see without spectacles is 50 cm.
Solution:
Image is formed at focus. We know that Power
$ (P)=frac{text{1}}{text{focal},text{length},text{(m)}} $ Given $ P=-2D $
$ therefore $ $ text{Focal},text{length},=-frac{1}{2}=-0.5,m $
$ Rightarrow $ $ F=-50,cm $
Hence, maximum distance of an object, which he can see without spectacles is 50 cm.