A rod AB of length 5 cm lies along the principal axis of the concave mirror of focal length 15 cm in such a way that the end closer to the pole is 30 cm away from it. Find the length of the image.

Explanation

To solve the problem of finding the length of the image of a rod AB placed along the principal axis of a concave mirror, we will follow these steps:

### Step 1: Understand the Setup
We have a concave mirror with a focal length (f) of 15 cm. The rod AB has a length of 5 cm, and one end (point A) is 30 cm away from the pole of the mirror. Therefore, the distance of point A from the mirror is -30 cm (using the sign convention where distances measured against the direction of incident light are negative).

### Step 2: Determine the Position of Point B
Since the length of the rod AB is 5 cm, the position of point B can be calculated as follows:
- Distance of point A from the mirror = -30 cm
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