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Correct Answer: D. Diverges, converges
In optics, this is a fundamental question that helps distinguish between two key types of lenses — concave and convex. A concave lens diverges rays of light, meaning it spreads them out. On the other hand, a convex lens converges rays of light, bringing them together at a focal point. Let’s explore why this happens and how it’s important in real-life applications.
Understanding Light Behavior Through Lenses
Lenses work on the principle of refraction — the bending of light as it passes through different media. Their shape determines how they bend light:
- Concave Lens (Diverging Lens): A concave lens is thinner at the center and thicker at the edges. When parallel rays of light strike its surface, they spread out or diverge after refraction. However, if we trace these diverging rays backward, they appear to come from a single point — called the focal point, located on the same side of the lens as the incoming rays. This is why a concave lens always forms a virtual, erect, and diminished image.
- Convex Lens (Converging Lens): A convex lens is thicker at the center and thinner at the edges. It bends incoming parallel rays towards each other, causing them to meet at a single point known as the principal focus on the opposite side. This is why a convex lens can form real and inverted images, depending on the object’s distance from the lens.
Why This Matters in Physics
This question is more than just a memory check — it’s foundational to understanding optical devices. Concave lenses are used in spectacles for correcting myopia (nearsightedness), while convex lenses are used in magnifying glasses, microscopes, and cameras due to their focusing ability.
Quick Tip for Students
A simple way to remember this:
Concave = Cave = Bends light outward = Diverges
Convex = Bulges out = Bends light inward = Converges
Common Doubts in Physics
