A screen is placed 90cm from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20cm. Determine 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 placed between them at two different locations separated by a distance 20 cm. Determine the focal length of the lens.

An object is placed at a distance of 1.5 m from a screen and a convex lens is interosed between them .the magnification produced is 4.What is the focal length of the lens?

If the distance between the screen and object is 50 cm and the displacement of the lens is 10 cm,clculate the focal length of the lens.

A convex lens is used to obtain a magnified image of an object on a screen 10 m from the lens .If the magnification is 19,find the foal length of the lens.

A needle placed 45cm from a lens forms an image on the screen placed 90cm on the other side of the lens. What is the type of lens ? Find the focal length. If the length of needle is 5cm. What is the length of image ?

A ocnverging bem of light forms of a sharp image on a screen. lens is placed in the path of the beam at 10 cm from the screen.It si found that screen has to be moved 8 cm further away from the lens to obtain a sharp image.Find the focal length and natrue of the lens.

Two lenses convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm, if they are placed 8.0 cm apart with their principal axes coincident. An object 1.5 cm in size is placed on the side of the convex lens. The distance between the object and the convex lens is 40 cm. Determine the magnification produced by the two-lens system, and the size of the image.