Two coaxial thin lenses are placed in contact with each other and a small object is placed at a distance of 20cm from the combination of lenses. The focal length of each lens is 30 cm. What will be the distance between the object and the image when both the lenses are (i) convex (ii) concave

Explanation

To solve the problem, we need to find the distance between the object and the image for two cases: when both lenses are convex and when both lenses are concave.

### Given:
- Object distance (u) = -20 cm (object distance is taken as negative in lens formula)
- Focal length of each lens (f1 = f2) = +30 cm for convex lenses and -30 cm for concave lenses.

### Part (i): Both Lenses are Convex

...