Suppose you have focused on a screen the image of candle flame placed at the farthest end of the laboratory table using a convex lens. If your teacher suggests you to focus the parallel rays of sun, reaching your laboratory table, on the same screen, what you are expected to do is to move the:

Options

A. lens slightly towards the screen
B. lens slightly away from the screen
C. lens slightly towards the sun
D. lens and screen both towards the sun

Explanation

To solve the question, we need to understand the behavior of a convex lens when focusing on different objects, specifically a candle flame and parallel rays from the sun.

### Step-by-Step Solution:

1. **Understanding the Setup**:
- Initially, you have focused the image of a candle flame on a screen using a convex lens. The candle flame is placed at the farthest end of the laboratory table, which means it is relatively close to the lens.

2. **Identifying the Image Formation**:
- When the candle flame is placed beyond the center of curvature (C) of the lens, the image is formed between the focus (F) and C. This is because a convex lens converges light rays that are coming from a point source (the candle flame).

3. **Considering the Sun's Rays**:
- The rays from the sun are parallel because the sun is very far away compared to the size of the lens. When parallel rays of light pass through a convex lens, they converge at the focus (F) of the lens.

4. **Adjusting the Lens or Screen**:
- To focus the parallel rays of the sun onto the same screen, you need to position the screen at the focus of the lens. Since the candle flame was focused when it was placed at a distance, the screen is currently positioned further away than the focus.

5. **Moving the Lens or Screen**:
- To achieve the focus of the sun's rays, you can either move the screen towards the lens or move the lens towards the screen. However, it is more practical to move the lens towards the screen.

6. **Conclusion**:
- Therefore, to focus the parallel rays of the sun onto the same screen, you are expected to move the lens towards the screen.

### Final Answer:
You are expected to move the lens towards the screen.

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