Size of image of an object by a mirror having a focal length of `20 cm` is observed to be reduced to `1/3 rd` of the size ? At what distance the object has been placed from the mirror ? What is the nature of the image and the mirror ?

Explanation

To solve the problem, we need to determine the distance at which the object is placed from the mirror, given that the size of the image is reduced to one-third of the size of the object. We will consider both concave and convex mirrors.

### Step-by-Step Solution:

**Step 1: Understand the given data**
- Focal length of the mirror (f) = 20 cm
- Magnification (m) = 1/3 (since the image is reduced to one-third of the object size, we take m = -1/3 for the sign convention)

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