The linear magnification of an object placed on the principal axis of a convex lens offocal length 30cm is found to be +2. In order to obtain a magnification of -2, by how much distance should the object be moved?

Explanation

To solve the problem, we need to find the distance the object must be moved in order to change the magnification from +2 to -2 for a convex lens with a focal length of 30 cm.

### Step-by-Step Solution:

1. **Understanding Magnification**:
The magnification (m) for a lens is given by the formula:
\[
m = \frac{v}{u}
...