A concave mirror is used in a solar furnace. (a) State the property of image formation by a concave mirror that makes it suitable for this application. (b) What must be true about the position of the Sun relative to the mirror for this property to be utilized? Explain.
Generated by claude-sonnet-4-6 · 2026-06-26 01:12 · grounding rag
Model Answer
(a) A concave mirror converges parallel rays of light to meet at its principal focus, producing a very high concentration of heat energy at that point. This property of focusing parallel light rays makes it suitable for a solar furnace.
(b) The Sun must be at (or effectively at) infinity from the mirror. Since the Sun is extremely far away, the rays coming from it are nearly parallel. When these parallel rays fall on the concave mirror, they all converge at the principal focus F, generating intense heat sufficient to act as a furnace.
Source: Chapter 9, Section 9.2.2 — Uses of concave mirrors
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Explanation
- (a) targets the optical property: concave mirror converges parallel rays at focus. Examiners expect the word "converge" or "concentrate" and mention of the principal focus.
- (b) targets Table 9.1: object at infinity → image at focus F. The key logic is Sun ≈ infinity ⇒ rays are parallel ⇒ all focus at F. Always link the position of the Sun (at infinity) to the resulting parallel rays.
- This question maps directly to Exercise Q8(c) in the textbook, so knowing "large concave mirrors concentrate sunlight to produce heat" is essential.