Young's Double Slit

Also called

double slit experiment · interference of light · coherent sources · interference fringes · fringe width · path difference · constructive interference · destructive interference · bright fringe · dark fringe · superposition of waves · Thomas Young · monochromatic light · wave optics · यंग का द्वि-झिरी प्रयोग · व्यतिकरण · फ्रिंज

Topics

• Two slits lit by one source act as coherent sources: their waves keep a constant phase difference.
• Where crest meets crest the waves add up (constructive); where crest meets trough they cancel (destructive).
• Bright fringe: path difference = nλ (n = 0, 1, 2…); dark fringe: path difference = (n + ½)λ.
• Fringe width β = λD/d, where D is the slit-to-screen distance and d the separation of the slits.
• Closer slits (smaller d) or a farther screen give wider fringes; red light gives wider fringes than violet.
• For one colour all the bright fringes are equally wide and equally bright.
• In white light the central fringe is white and the side fringes are coloured, violet inside and red outside.
• Interference only redistributes light energy on the screen; it does not create or destroy it.

About this model

A GLB file of about 386 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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