Which of the following is NOT a characteristic of a plus lens?

• A. With motion
• B. Converging light rays
• C. Positive focal length
• D. Thicker at the center

Answer: (A)

The characteristic that is not associated with a plus lens is that it exhibits with motion. Plus lenses, which are convex, are known for their ability to converge light rays, have a positive focal length, and are typically thicker in the center compared to their edges.

When light rays pass through a plus lens, they bend toward the optical axis, converging at a point known as the focal point. This property is key to how plus lenses are used in optics, particularly for correcting hyperopia or hyperopia-related vision issues. The positive focal length indicates that the focal point lies on the same side as the light source, which is another defining feature of plus lenses. Additionally, the thickness at the center reinforces their converging design, as the center of the lens is thicker to aid in bending the incoming light rays toward one another.

In contrast, the term "with motion" typically refers to the phenomenon observed when viewing objects through certain types of lenses, particularly with minus or concave lenses, which exhibit a divergence of light rays and can create the illusion of movement in the opposite direction (a characteristic known as "against motion"). Therefore, "with motion" does not describe the inherent physical properties or characteristics of a plus lens.