Focus of concave and convex mirrorsअवतल और उत्तल दर्पण का फोकसFocus of concave and convex mirrors

NCERT Fig 9.3 · Class 12 Physics · Chapter 9 · interactive diagram

Parts and what they mean

• Concave mirror (अवतल दर्पण) — A reflecting surface that is part of a hollow sphere, silvered on the outside so it reflects from the inside (curved in towards the object). Converging.
• Convex mirror (उत्तल दर्पण) — Reflecting surface bulges towards the object. Diverging; f is positive.
• Parallel paraxial rays (concave) (समांतर उपाक्षीय किरणें (अवतल)) — Traced exactly with the law of reflection (normal along the radius). Near the axis they all cross at F.
• Parallel rays (convex) (समांतर किरणें (उत्तल)) — After reflection they spread out; produced backwards (dashed) they meet at F behind the mirror.
• Real focus F (वास्तविक फोकस F) — Rays actually meet here. For a concave mirror f is negative (F is in front, against the incident light).
• Virtual focus F (आभासी फोकस F) — Rays only appear to come from here. For a convex mirror f is positive.
• Pole P (ध्रुव P) — Geometric centre of the mirror surface. All distances are measured from P.
• Focal length f (फोकस दूरी f) — Distance PF = R/2 (for paraxial rays).
• Principal axis (मुख्य अक्ष) — The line through the pole P and the centre of curvature C.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 9.3. Report a mistake