When an object approaches a convex lens from infinity, the image formed by it shifts

Options

A. away from the lens
B. towards the lens
C. first away and then towards the lens
D. none of these

Answer

To solve the question about how the image formed by a convex lens shifts when an object approaches it from infinity, we can analyze the situation step by step.

### Step-by-Step Solution:

1. **Understanding the Convex Lens**: A convex lens converges light rays that are coming from a distance. When an object is placed at infinity, the light rays coming from it are parallel.

2. **Object at Infinity**: When the object is at infinity, the image is formed at the focal point (F) of the lens. This means that the image distance (v) is equal to the focal length (f) of the lens.

- **Image Distance (v)**: v = f

3. **Object at Center of Curvature (C)**: As the object moves closer to the lens, when it is at the center of curvature (C), the image is formed at the same distance on the opposite side of the lens (C').

- **Image Distance (v)**: v = C

4. **Object at Focal Length (F)**: If the object is placed at the focal point (F), the rays coming from the object will emerge parallel after passing through the lens, resulting in the image being formed at infinity.

- **Image Distance (v)**: v = ∞

5. **Analyzing the Shift**: As the object moves from infinity to the focal point:
- Initially, the image is at the focal point (f).
- Then, as the object moves towards the lens from infinity to C, the image distance (v) increases from f to C.
- Finally, as the object approaches the focal point (F), the image distance (v) becomes infinite.

6. **Conclusion**: Therefore, as the object approaches the lens from infinity, the image formed shifts away from the lens until it reaches the focal point, and then it continues to shift towards infinity as the object approaches the focal point.

### Final Answer:
The correct option is: **First option - away from the lens.**

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