PhysicsChapter 4: Diffraction and Interference
Fringe Spacing in Young's Experiment
Fringe spacing
Definition
Fringe spacing is the distance between successive bright fringes or successive dark fringes in Young’s double-slit interference pattern.
Dependence
For bright fringes: yn=nλD/d Next bright fringe: y(n+1)=(n+1)λD/d Therefore fringe spacing: β = y(n+1)−yn Thus: β=λD/d `β ∝ λ` Longer wavelength → wider fringes. `β ∝ D` Screen farther away → wider fringes. `β ∝ 1d` Greater slit separation → narrower fringes.
Bright-to-Nearest-Dark Distance
Since dark fringes lie halfway between bright fringes: **distance = β/2**
Formula / Key Relation
**β=λD/d**
Exam preparation
Exam Focus
Quick revision
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Review the key facts, formulas and checks before you move on.Fringe Spacing in Young's Experiment
Sticky Notes · Quick Revision
Fringe width:
- `β = λD/d`
- Wider:
- λ ↑
- D ↑
- Narrower:
- d ↑
60-second revision
- Fringe spacing is constant in the ideal small-angle double-slit pattern.
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