An object is placed between the pole and the principal focus of a concave mirror. Using standard ray diagram rules, describe how the image is formed and state the nature, position, and size of the image obtained.
Generated by claude-sonnet-4-6 · 2026-06-26 01:10 · grounding rag
Model Answer
When an object is placed between the pole (P) and the principal focus (F) of a concave mirror, two rays are used to locate the image:
- A ray parallel to the principal axis, after reflection, passes through the principal focus F.
- A ray directed towards the centre of curvature, after reflection, returns along the same path.
The two reflected rays diverge and do not meet in front of the mirror. When extended behind the mirror, they appear to meet at a point behind the mirror.
Nature, Position, and Size of Image:
- Position: Behind the mirror (beyond the pole)
- Nature: Virtual and erect
- Size: Enlarged (magnified)
(Refer to Table 9.1 — object between P and F)
Source: Chapter 9, Section 9.2.2 & Table 9.1
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Explanation
- The key fact examiners want: reflected rays diverge → image forms behind the mirror by extending rays backward → hence virtual.
- Three properties must all be stated: position (behind mirror), nature (virtual and erect), size (enlarged). Missing any one loses a mark.
- Mentioning the two specific ray rules used in the diagram earns full credit for the "describe how image is formed" part.
- This is the only case where a concave mirror gives a virtual, erect, and magnified image — useful to remember for MCQs too (Exercise Q2 of the chapter).