A convex lens is placed at a distance of 40 cm from a screen. A point source is placed at a distance of 60 cm from the screen on the same side of the lens. At this position of point-source, a circular spot of light of diameter equal to the lens is formed. Show the formation of image by a ray diagram. Up to what distance the source be displaced so that its clear image can be formed on the screen?

Explanation

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have a convex lens placed 40 cm away from a screen.
- A point source is located 60 cm from the screen on the same side as the lens.

2. **Identifying Distances**:
- Distance from the lens to the screen (v) = 40 cm.
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