Question

a person connect see objects clearly which are placed before 40 cm from him ,the power of the lens to correct the vision is
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Answer 1

Explanation:

That lens should be given to the person which forms the image of an object at infinity at distance 40 cm in front of the eye.

Hence, u=−∞ and v=−40cm

Now,

f1=v1−u1

⟹f1=40−1−−∞1

⟹f=−40cm

P=f(cm)100=40−100=

⟹P=−2.5D