Q1. [3] deep thorough-understanding
You hold the inner (concave) surface of a shining spoon close to your face and observe your reflection. As you slowly move the spoon farther away from your face, the image undergoes a noticeable change at one particular distance and then changes again beyond it. (i) Describe the nature, size, and orientation of the image at each stage of this sequence. (ii) Explain why the image changes at that particular distance.
Generated by claude-sonnet-4-6 · 2026-06-26 01:12 · grounding rag
Model Answer
(i) Image at each stage (concave/inner surface of spoon):
- Very close (between P and F): Image is virtual, erect, and enlarged — face appears magnified.
- At focal point F: No image is formed; reflected rays are parallel.
- Beyond F (object between F and C, at C, or beyond C): Image is real, inverted, and the size varies — enlarged (between F and C), same size (at C), or diminished (beyond C).
(ii) Reason for the change:
The critical change occurs when the face crosses the focal point (F) of the concave mirror. Inside F, the reflected rays diverge and appear to come from behind the mirror (virtual image). Beyond F, reflected rays actually converge in front of the mirror to form a real, inverted image. The focal point is thus the boundary where image nature flips from virtual & erect to real & inverted.
Source: Chapter 9, Section 9.2.1, Table 9.1
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Explanation
- Examiners expect all three stages to be addressed with nature, size, and orientation for each — use Table 9.1 as your reference.
- The key phrase is: focal point is the boundary between virtual-erect and real-inverted images — this directly answers part (ii).
- Avoid writing long paragraphs; bullet-point stages are cleaner and score better for this type of question.