Concave mirror: pole, centre of curvature, focusअवतल दर्पण: ध्रुव, वक्रता केंद्र, मुख्य फोकस

NCERT Fig 9.2 (a) · interactive diagram

Parts and their functions

• Concave mirror (अवतल दर्पण) — Reflecting surface curved inwards, towards the centre of the sphere. It converges light.
• Pole (P) (ध्रुव (P)) — Centre of the reflecting surface. All distances are measured from here.
• Centre of curvature (C) (वक्रता केंद्र (C)) — Centre of the sphere of which the mirror is a part. It lies in front of a concave mirror.
• Principal focus (F) (मुख्य फोकस (F)) — Rays parallel to the principal axis meet here after reflection. Midway between P and C.
• Principal axis (मुख्य अक्ष) — Straight line through the pole and the centre of curvature; normal to the mirror at the pole.
• Radius of curvature (R) (वक्रता त्रिज्या (R)) — Radius of the sphere: R = distance PC. Any line from C to the mirror is a normal.
• Focal length (f) (फोकस दूरी (f)) — Distance PF. For small apertures, R = 2f.
• Aperture (द्वारक) — Diameter of the reflecting surface. NCERT takes the aperture much smaller than R.
• Rays parallel to the principal axis (मुख्य अक्ष के समांतर किरणें) — After reflection from a concave mirror they converge to the principal focus F.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 9.2 (a). Report a mistake