A convex lens is placed between object and a screen. The size of object is $3cm$ and an image of height $9cm$ is obtained on the screen. When the lens is displaced to a new position, what will be the size of image on the screen?

Q. A convex lens forms an image of an object on a screen. The height of the image is 9 cm. The lens is now displaced until an image is again obtained on the screen. The height of this image is 4 cm. The distance between the object and the screen is 90 cm.

Q. A convex lens forms a real image $9cm$ long on a screen. Without altering the position of the object and the screen, the lens is displaced and we get again a real image $4cm$ long on the screen. Then the length of the object is-

Q. A convex lens makes a real image $4cm$ long on a screen. When the lens is shifted to a new position without disturbing object or the screen, we again get a real image on the screen which is $9cm$ long. The length of the object must be :

Q. A screen is placed 90 cm from an object . The image of the object on the screen is formed by convex lens at two different locations separated by 20 cm . Determine the focal length of the lens (b) suppose the object has a size of 10 cm, and in one case the image is half of its size. Determine image size when lens is displaced to second position