Total internal reflection and critical angleपूर्ण आंतरिक परावर्तन और क्रांतिक कोणTotal internal reflection and critical angle

NCERT Fig 9.11 · Class 12 Physics · Chapter 9 · interactive diagram

Parts and what they mean

• Denser medium (water) (सघन माध्यम (जल)) — Light travels from here towards the rarer medium. TIR is possible only in this direction.
• Rarer medium (air) (विरल माध्यम (वायु)) — Refracted rays bend away from the normal (r > i).
• Point source A (बिंदु स्रोत A) — Sends rays to the surface at increasing angles of incidence.
• Small i: partly refracted, partly reflected (छोटा i: आंशिक अपवर्तन, आंशिक परावर्तन) — Most light goes out into the air; a weak ray (thin) reflects back.
• Larger i: r larger still (बड़ा i: r और बड़ा) — As i increases, r increases faster and the refracted ray leans towards the surface.
• i = ic: refracted ray grazes the surface (i = ic: अपवर्तित किरण सतह को छूती हुई) — At the critical angle, r = 90°.
• i > ic: total internal reflection (i > ic: पूर्ण आंतरिक परावर्तन) — No refraction is possible; all the light is reflected back into the water (no loss to transmission).
• Critical angle ic (क्रांतिक कोण ic) — Angle of incidence (in the denser medium) for which the angle of refraction is 90°: sin ic = n₂₁ = 1/n. Water 48.75°, crown glass 41.14°, diamond 24.41°.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 9.11. Report a mistake