A thin rod of length `f//3` is placed along the optic axis of a concave mirror of focal length f such that its image which is real and elongated, just touches the rod. The magnification is `"_____________"`

Explanation

To solve the problem, we need to find the magnification of the image formed by a concave mirror when a thin rod of length \( \frac{f}{3} \) is placed along the optic axis. The image is real and elongated, and it just touches the rod.

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Length of the rod \( L = \frac{f}{3} \)
- Focal length of the concave mirror \( f \) (negative for concave mirrors)

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