Question

A convex lens produces an inverted image 29 cm from the lens, when an object is placed 1.7 m in front of the lens. At what distance should the object be placed to produce an upright image of 2.2 times the size as the object?

Answer 1

First find the focal length of lens using lens formula.
Taking the distances in the direction of the movement of light to be positive and origin at optical center.
Image distance, v=29cm
Object distance, u=-170cm
Here we used the fact that inverted image (real image) is formed on the opposite side of lens.Use this information to find the focal length.

Now that you know the focal length, we can use the lens formula again to calculate the object distance to produce the given magnification.