Q1. [3] medium thorough-understanding
A candle placed in front of a plane mirror produces a virtual, erect image of the same size as the object. If the same candle is now placed between the pole and the principal focus of a concave mirror, compare the image formed with that in the plane mirror. State any TWO properties of the image that differ and explain the optical reason behind each difference.
Generated by claude-sonnet-4-6 · 2026-06-26 01:11 · grounding rag
Model Answer
Plane mirror: Virtual, erect, same size as object.
Concave mirror (object between P and F): Virtual, erect, but enlarged (magnified).
Two properties that differ:
- Size of image: The concave mirror forms an enlarged image, whereas the plane mirror forms an image of the same size. This is because the concave mirror's curved reflecting surface converges reflected rays such that they appear to diverge from a point behind the mirror farther apart, producing magnification greater than 1.
- Position of image: In a plane mirror, the image is as far behind the mirror as the object is in front. In a concave mirror (object between P and F), the image forms behind the mirror at a greater distance than the object distance, due to the focusing action of the curved surface.
Source: Chapter 9, Table 9.1; Section 9.1
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Explanation
- The key fact from Table 9.1: object between P and F → image is behind the mirror, virtual, erect, and enlarged. This is the critical difference from a plane mirror (same size, image distance = object distance).
- Examiners expect you to name the two differing properties clearly and give the optical reason for each. Don't just list properties — explain why (curved surface → convergence → magnification >1).
- "Virtual and erect" is common to both, so don't list those as differences.