Science (086) — AI-generated practice question

A convex lens is thicker in the middle than at the edges. When parallel rays pass through it, the thicker central portion refracts the rays inward, causing them to converge at a point called the principal focus — hence it is a converging lens.

A concave lens is thicker at the edges than in the middle. When parallel rays pass through it, the thicker edges refract the rays outward, causing them to diverge — appearing to spread out from a principal focus on the same side as the incident light — hence it is a diverging lens.

Source: Chapter 9, Section 9.3.3 — Refraction by Spherical Lenses

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• The key physical feature examiners look for is the shape/thickness profile of each lens — thicker at middle (convex) vs. thicker at edges (concave).
• Link the shape directly to the behaviour: thick middle → converges; thick edges → diverges.
• Mention "principal focus" to show understanding of refraction outcome.
• Do not just say "curved surfaces" — be specific about where the lens is thicker, as that is what drives the answer.