To construct a ray diagram, you need at least ______ whose path(s) after refraction through the lens are known.

Options

A. one ray
B. two rays
C. three rays
D. none of these

Explanation

To construct a ray diagram, you need at least **two rays** whose paths after refraction through the lens are known.

### Step-by-Step Solution:

1. **Understanding Ray Diagrams**:
- A ray diagram is a graphical representation used to show the path of light rays as they pass through optical devices like lenses and mirrors.

2. **Identifying the Minimum Requirement**:
- To accurately determine the position of the image formed by a lens, we need to know the paths of light rays after they refract through the lens.

3. **Determining the Number of Rays Needed**:
- At least two rays are required to find the point where they converge or diverge to form an image. If we only have one ray, we cannot determine the exact location of the image.

4. **Example of Ray Paths**:
- One common approach is to use:
- A ray that travels parallel to the principal axis, which, after refraction, will pass through the focus of the lens.
- A second ray that travels through the optical center of the lens, which will continue in a straight line without deviation.

5. **Conclusion**:
- The intersection of these two rays will give us the position of the image. Therefore, the minimum number of rays needed to construct a ray diagram is **two**.