Young’s double-slit arrangement and the path difference at Pयंग का द्वि-झिरी प्रयोग और P पर पथांतरYoung’s double-slit arrangement and the path difference at P
NCERT Fig 10.12 · Class 12 Physics · Chapter 10 · interactive diagram
Parts and what they mean
- Source pinhole S (स्रोत पिनहोल S) — One pinhole lit by a bright source. Light from S reaches both S₁ and S₂ — this “locks” their phases.
- Two pinholes / slits S₁, S₂ (दो पिनहोल / झिरियाँ S₁, S₂) — Derived from the same source, so any phase jump in S appears equally in both: S₁, S₂ are coherent.
- Wavefronts (तरंगाग्र) — Spherical waves spread from S, and then from S₁ and S₂, and overlap.
- Slit separation d (झिरियों की दूरी d) — Typically a fraction of a millimetre.
- Slit–screen distance D (झिरी–पर्दा दूरी D) — D ≫ d (often about 1 m).
- Paths S₁P and S₂P (पथ S₁P और S₂P) — Waves from S₁ and S₂ travel different distances to P.
- Path difference (पथांतर) — S₂P − S₁P ≈ xd/D (for x, d ≪ D). Bright when xd/D = nλ, dark when xd/D = (n + ½)λ.
- Distance x of P from O (O से P की दूरी x) — Measured on the screen from the central point O.
- Point P on the screen (पर्दे पर बिंदु P) — Where we find the intensity.
- Central point O (केंद्रीय बिंदु O) — S₁O = S₂O: path difference 0 → central bright fringe.
- Perpendicular bisector (लंब समद्विभाजक) — Every point on it is equidistant from S₁ and S₂.
- Screen GG′ (पर्दा GG′) — Fringes appear here.
Original diagram drawn by Simple Learning Hub, based on NCERT Fig 10.12. Report a mistake