Long-sightedness is caused by the eyeball being too short. It can be corrected by the use of a

Options

A. convergent lens
B. plane mirror
C. divergent lens
D. none of these

Answer

### Step-by-Step Solution:

1. **Understanding Long-Sightedness**:
- Long-sightedness, also known as hyperopia, occurs when the eyeball is too short. This condition prevents the eye from focusing on nearby objects clearly, while distant objects may be seen more clearly.

2. **Identifying the Cause**:
- In long-sightedness, the image of an object is formed behind the retina. This happens because the distance from the lens of the eye to the retina is shorter than necessary for clear vision.

3. **Determining the Corrective Measure**:
- To correct long-sightedness, we need to bring the image forward so that it falls directly on the retina. This can be achieved by using a lens that converges light rays.

4. **Choosing the Right Lens**:
- The appropriate lens for correcting long-sightedness is a **convex lens** (also known as a converging lens). A convex lens has the ability to bend light rays inward, allowing the image to be formed at the correct position on the retina.

5. **Conclusion**:
- Therefore, long-sightedness can be corrected by the use of a **convex lens**.