Draw ray diagram showing the image formation by a convex lens when an object is placed at the focus of the lens.

Explanation

To solve the problem of drawing a ray diagram showing the image formation by a convex lens when an object is placed at the focus of the lens, we can follow these steps:

### Step-by-Step Solution:

1. **Draw the Convex Lens**:
- Start by drawing a vertical line to represent the convex lens. The lens should be thicker in the middle and thinner at the edges.

2. **Mark the Principal Axis**:
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