The magnification produced by a spherical mirror is –3. What does the negative sign tell you, and what does the magnitude 3 tell you? In what region in front of the mirror must the object be placed to produce this image?
Generated by claude-sonnet-4-6 · 2026-06-26 01:13 · grounding rag
Model Answer
Negative sign: A negative magnification indicates that the image is real and inverted (formed in front of the mirror).
Magnitude 3: The image is 3 times enlarged compared to the object (height of image = 3 × height of object).
Position of object: For a concave mirror to produce a real, inverted, and enlarged image (|m| > 1), the object must be placed between the centre of curvature (C) and the focus (F) of the concave mirror.
Source: Chapter 9, Section 9.2.4 Mirror Formula and Magnification
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Explanation
- The sign of magnification tells nature + orientation: negative → real + inverted; positive → virtual + erect.
- The magnitude tells the size ratio: |m| = 3 means image is three times the object size.
- Examiners expect all three parts answered: sign meaning, magnitude meaning, and object position. Missing the object-position part loses a mark.
- Remember: only a concave mirror can give m = –3 (real, enlarged image), achieved when the object is between F and C.