An object is placed between a wall and a concave mirror of focal length 15 cm. The distance between wall and mirror is 40 cm. Find the position of the object placed such that the image of the object is just formed on the wall.

Explanation

To solve the problem, we will use the mirror formula and the given information about the concave mirror and the distances involved.

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have a concave mirror with a focal length (f) of -15 cm (negative because it is a concave mirror).
- The distance between the wall and the mirror is 40 cm.
- We need to find the position of the object (u) such that the image (v) is formed on the wall.
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