Image Formation by Lenses

In order to use a convex lens as a magnifying glass, where should the object be placed?

If we wish to obtain an image thrice as large as the object using a converging lens of focal length $20 \mathrm{cm}$, the object distance should be

A convex lens was used to form images of an object kept at different positions. The object positions used were $120 \mathrm{cm}, 60 \mathrm{cm}, 40 \mathrm{cm}, 30 \mathrm{cm}$ and $25 \mathrm{cm}$. The image positions, not necessarily in correct order, were $40 \mathrm{cm}, 24 \mathrm{cm}, 100 \mathrm{cm}, 30 \mathrm{cm}$ and $60 \mathrm{cm}$.

Which position of the object among the given positions will give the largest image?

A convex lens was used to form images of an object kept at different positions. The object positions used were $120 \mathrm{cm}, 60 \mathrm{cm}, 40 \mathrm{cm}, 30 \mathrm{cm}$ and $25 \mathrm{cm}$. The image positions, not necessarily in correct order, were $40 \mathrm{cm}, 24 \mathrm{cm}, 100 \mathrm{cm}, 30 \mathrm{cm}$ and $60 \mathrm{cm}$.

Find the focal length of the lens.

A convex lens was used to form images of an object kept at different positions. The object positions used were $120 \mathrm{cm}, 60 \mathrm{cm}, 40 \mathrm{cm}, 30 \mathrm{cm}$ and $25 \mathrm{cm}$. The image positions, not necessarily in correct order, were $40 \mathrm{cm}, 24 \mathrm{cm}, 100 \mathrm{cm}, 30 \mathrm{cm}$ and $60 \mathrm{cm}$. Write the correct order of the image distances.

A thin converging lens forms a (i) real magnified image; (ii) virtual magnified image of an object placed in front of it.

(a) Write the positions of the objects in each case.

(b) If the lens is now cut into two halves along the principal axis, how will the focal length and the intensity of image formed by half lens be affected?

Match the descriptions of images formed by a convex lens in Column I to the object positions in Column II.

A concave lens can concentrate sun's rays to a point and burn a hole in a piece of paper.

Things always look smaller on viewing through a convex lens.

_____ lenses always produce an erect and diminished image.

A _____ lens can form both real and virtual images.

The image formed by a concave lens is

A convex lens is used to obtain a real image of an object. What change would you make to obtain an image nearer to the lens?

What will be the distance between an object and its image if it is given that the image of the same size as the object is formed by a convex lens of focal length $12 \mathrm{cm}$?

At what distance from a convex lens of focal length $12 \mathrm{cm}$, should an object be placed so that the lens forms an image of the same size as the object?

When a small-lighted bulb is kept at the focus of a convex lens, the lens produces

A converging lens forms a virtual image of an object when the object is placed at a distance of $19 \mathrm{cm}$ from it. The focal length of the lens must be

A $2 \mathrm{cm}$ high object is placed at a distance of $2 f$ from a convex lens. The height of image formed will be

With the help of ray diagrams, show the formation of image of an extended object by a concave lens for all possible positions of the object. State the position, nature and size of image formed, for each case.

Which optical instrument uses the arrangement of the convex lens mentioned in (b)?