Where should an object be kept if a real image is obtained at a distance 60 cm from a concave lens of focal length 20 cm. Is the object real or virtual?

Explanation

To solve the problem, we will use the lens formula and analyze the situation step by step.

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Focal length (f) of the concave lens = -20 cm (negative because it is a concave lens).
- Distance of the real image (v) = -60 cm (negative because, for a real image formed by a concave lens, the image distance is measured in the opposite direction).

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