What is minimum distance between an object and the real image formed by a convex lens?

The following data was recorded for values of object distance and the corresponding values of image distance in the experiment on study of real image formation by a convex lens of power +5 D.One of these observations is incorrect.Identify this observation and give reason for your choice: .

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.

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.

How is image formed by a concave lens? Show by drawing diagram as to what will be the position and nature of the image formed by a concave lens?

Draw the ray diagrams and find position,nature and size of image formed by a convex lens,when object is placed: between F and 2F

Draw the ray diagrams and find position,nature and size of image formed by a convex lens,when object is placed:At F.

What is the distance between object and eye lens, when the telescope is on normal adjustment?

Draw the ray diagrams and find position,nature and size of image formed by a convex lens,when object is placed: beyodn 2 F

A convex lens of focal length 0.12 m produces an inverted image ,which is three times as long as the object.Find the distance between the object and the lens for a real image.