ABO NOCE Practice Test

What determines the movement of light rays in a plus lens?

1. The curvature of the lens

2. The density of the lens material

3. The color of the lens

4. The age of the lens

The correct answer is: The curvature of the lens

The movement of light rays in a plus lens is primarily determined by the curvature of the lens. A plus lens, which is convex, has a specific shape that causes incoming parallel light rays to converge at a focal point. The degree to which the light rays are bent, or refracted, as they pass through the lens depends on the curvature; a more pronounced curve will typically lead to a stronger converging effect. The curvature influences the angles at which light rays enter and exit the lens, effectively controlling the focal length—the distance from the lens to the point where the light converges. This property is crucial for various applications, particularly in corrective eyewear for hyperopia (farsightedness), where the lens helps the eye focus light correctly onto the retina. While factors such as the density of the lens material can also affect how light is refracted (with denser materials typically causing more bending of light), it is mainly the curvature that defines the fundamental behavior and movement of light in a plus lens. The color or age of the lens does not affect its optical function in the same way that curvature does, making these options less relevant in determining the behavior of light rays through the lens.