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 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 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

When an object is placed at the proper distance ot the left of a converging lens, the image is focused in a screen 30 cm to the right of lens. A dieverging lens is now placed 15 cm to the right of the converging lens and it is found that the screen must be moved 19.2cm farther to the right to obtain a sharp image. Find the focal length of the diverging lens.

When an object is placed at the proper distance ot the left of a converging lens, the image is focused in a screen 30 cm to the right of lens. A dieverging lens is now placed 15 cm to the right of the converging lens and it is found that the screen must be moved 19.2cm farther to the right to obtain a sharp image. Find the focal length of the diverging 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 :

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 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

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 ?