Power of a Lens

The following data-was recorded for values of object distance and the corresponding values of image distance in the experiment on study of real image formation by a convex lens of power $+5 \mathrm{D}$.

The power of lens depends on the focal length of the lens.

If the powers of the lenses $L_1, L_2$ are in the ratio of $4:1$, what would be the ratio of the focal length of $L_1, L_2$?

Two thin lenses of focal length $f_1$and $f_2$ are in contact and coaxial. Its power is the same as the power of a single lens given by

Focal length of a lens is $50 \mathrm{cm}$. In dioptre power of lens will be.

A man used a convex lens of focal length of $20 \mathrm{cm}$ in his specs, the power of this lens is:

The power of a plane mirror is :

The unit of power of a lens is $\mathrm{dioptre}$. Then $1 \mathrm{dioptre}$ is equal to :

Select the correct statement.

The focal length of a convex lens is $20 \mathrm{cm}$. Its power is :

A person can not clearly see objects at a distance more than 40 cm. He is advised to use lens of power

A person needs a lens of power $-4.5 \mathrm{D}$ for correction of his/her vision, then the focal length of corrective lens is.

The power of a lens is $-2.5 \mathrm{D}$. Its focal length is

Find the power of a concave lens of focal length $2 \mathrm{m}$?

Which of the following statements is true?

A person cannot see distinctly objects kept beyond $2 \mathrm{m}$. This defect can be corrected by using a lens of power

You are given two convex lenses $I$ and $II$ made of the same glass. $I$ is thicker than $II$ . Choose the correct answer from the following.

Which of the following statements is true?

A doctor has prescribed a corrective lens of power $+1.5 \mathrm{D}$. Find the focal length of the lens in meter. (round off up to two decimal places)

What do you mean by the power of the lens?