An object and a screen are placed 80 cm apart. There are two positions at which a convex lens forms a real image on the screen, the magnification in the cases being 3/2 and 2/3. Calculate the focal length of the lens.

An object is kept at 10 cm in front of a convex lens. Its imge is formed on the screen at 15 cm from the lens. Calculate the focal length of the lens.

A screen is placed 80 cm from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 10 cm . Calculate the focal length of the lens used.

A source of light and a screen are placed 90 cm apart. Where should a convex lens of 20 cm focal length be placed in order to form a real image of the source on the screen ?

(a) A screen is kept at a distance of 1m from the object. A converging lens between the object and the screen, when placed at any of the two positions which are 60cm apart, forms a sharp image of the object on the screen. Find the focal length of the lens. (b) In the two positions of the lens, lateral size of the image is 4cm and 9cm. Find the size of the object.

A screen is placed 90 cm from an object. The image of the object on the screen is formed by a convex lens at two different positions separated by 20 cm. Calculate the focal length of the lens.

Aluminous object and a screen are placed on an optical bench and a converging lens is placed between them to throw a sharp image of the object on the screen, the linear magnification of the image is found to be 2.5. The lens is now moved 30 cm nearer the screen and a sharp image is again formed. Calculate the focal length of the lens.

An object 50 cm tall is placed on the principle axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.

An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.

An object placed at 20 cm from a lens, forms an image on a screen placed 60 cm on the other side of the lens. What is the focal length and type of the lens ?