For the system given below,if the image of the object is formed on itself.What will be the focal length of the lens?

A convex lens forms a real image on a screen placed at a distance 60 cm from the object. When the lens is shifted towards the screen by 20 cm , another image of the object is formed on the screen. The focal length of the lens is :

Two point objects A and B are kept on the principal axis of a convex lens as shown. Image of both the objects is formed at same position. Find the focal length of the lens.

An object is kept at a distance of 16 cm from a thin lens and the image formed is real. If the object is kept at a distance of 6 cm from the lens, the image formed is virtual. If the sizes of the images formed are equal, the focal length of the lens will be

A convex lens forms an image of an object on a screen 30 cm from the lens. When the lens is moved 90 cm towards the object, then the image is again formed on the screen. Then, the focal length of the lens is

What should be the value of distance d so that final image is formed on the object itself. (Focal length of the lenses are written on the lenses.)

The graph in shows the variation of image distance (v) with object distance (u) in case of a lens. Find focal length of the lens. What is the nature of the lens, if image formed is real ? .

An object is 2m from a lens which forms an erect image one-fourth (exactly) the size of the object. Determine the focal length of the lens. What types of lens is this?

A convex lens is placed in contact with a plane mirror. An axial point object at a distance of 20 cm from this combination, has its image coinciding with itself. What is the focal length of the convex lens ?