Question

a person can't see clearly an object kept at a distance beyond of 100cm. find the nature and power of lens to be used for seeing clearly the object kept at infinity

please guys answer step by step

most important

Answer 1

concave lens is required.
Power of lens = 1/f
Here 1/1m (100 cm = 1m)
Power = 1 D

Answer 2

Answer: The correct answer is concave and the power of the lens is 1 D.

Explanation:

The expression for the lens formula is as follows;

$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

Here, v is the image distance, u is the object distance and f is the focal length.

It is given in the problem that a person can't see clearly an object kept at a distance beyond of 100 cm. The object is kept at infinity.

Put v= 100 cm and u = infinity.

$\frac{1}{f}=\frac{1}{100}-\frac{1}{infinity}$

$f=100 cm$

Calculate the power of the lens.

$P=\frac{1}{f(m)}$

Convert the focal length in meter.

Put f= 1 m.

$P=\frac{1}{1}D$

$P=1 D$

The power of the lens is positive. It means that it is a concave lens.

Therefore, the nature of the lens is concave and the power of the lens is 1 D.