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

A convex lens produces an image of a real object on a screen with a magnification of 1/2. When the lens is moved 30 cm away from the object, the magnification of the image on the screen is 2. The focal length of the lens is

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 :

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. Then height of this image is 4 cm . The distance between the object and the screen is 90 cm.

An object and a screen are mounted on an optical bench and a converging lens is placed between them so that a sharp image is obtained on the screen. The linear magnification of the image is 25. The lens is now moved 30 cm towards the screen and a sharp image is ■ again formed on the screen. Find the focal length of the lens

An object to the left of a lens is imaged by the lens on a screen 30cm to the right of the lens. When the lens is moved 5cm to the right, the screen must be moved 5cm to the left to refocus the images. The focal length of lens is :-

A convex lens when placed in the first position forms a real image of an object on a fixed screen. The distance between the object and the screen is 75 cm. On displacing the lens from first position by 25 cm to the second position, again a real image is formed on the screen. Then the focal length of the lens is

A convex lens is used to form image of an object on screen. When half of the lens is covered by painting black on it, then

A convex lens forms an image of an object on a screen ,The height of the image is 9cm The lens is now disiplaced between the object on the screen.the height of this image is 4cm .the distance between the object and the screen is 90cm

A convex lens forms a real and inverted image of a pencial at a distance of 60 cm from the lens. The image formed is of the same size as the object. Find the focal length and power of the lens. At what distance is the pencil placed from the lens. ?