A lens as two refracting surfaces (lens maker’s formula)लेंस: दो अपवर्तक पृष्ठ (लेंस मेकर सूत्र)A lens as two refracting surfaces (lens maker’s formula)

NCERT Fig 9.16 · Class 12 Physics · Chapter 9 · interactive diagram

Parts and what they mean

• Double convex lens (उभयोत्तल लेंस) — Bounded by two spherical surfaces of radii R₁ and R₂.
• Principal axis (मुख्य अक्ष) — Joins the two centres of curvature.
• First surface (R₁ positive) (पहला पृष्ठ (R₁ धनात्मक)) — Its centre C₁ is on the right (along the light), so R₁ = +BC₁. Acting alone, it would form the image I₁.
• Second surface (R₂ negative) (दूसरा पृष्ठ (R₂ ऋणात्मक)) — Its centre C₂ is on the left, so R₂ = −DC₂. It takes I₁ as a virtual object and forms the final image I.
• Ray from the object (वस्तु से किरण) — Bends at surface 1.
• Ray inside the glass (काँच के अंदर किरण) — Heads towards I₁.
• Towards I₁ (if surface 2 were absent) (I₁ की ओर (यदि पृष्ठ 2 न हो)) — With these numbers surface 1 alone would form I₁ about 45 cm away — far off the picture.
• Final refracted ray (अंतिम अपवर्तित किरण) — Bends again at surface 2 and meets the axis at I.
• Object O (वस्तु O) — Point object on the axis.
• Final image I (अंतिम प्रतिबिंब I) — Given by 1/v − 1/u = 1/f with 1/f = (n − 1)(1/R₁ − 1/R₂).

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 9.16. Report a mistake