PhysicsChapter 4: Diffraction and Interference
Young's Double-Slit Experiment
Young’s double-slit experiment
Definition
Young’s double-slit experiment demonstrates light interference by allowing coherent waves from two closely spaced slits to overlap on a screen and form alternating bright and dark fringes.
Bright Fringes
Monochromatic light illuminates two narrow slits separated by distance: d The screen is at distance: D where typically: D >> d Consider a point at angle `θ`. Path difference is approximately: Δr=d sinθ **d sinθ=nλ**
Dark Fringes
**d sinθ=(n+½)λ For small angles: sinθ≈tanθ≈yD Therefore bright-fringe position: yn=nλD/d Dark-fringe position: y=(n+½)λD/d** The pattern demonstrates the wave nature of light.
Formula / Key Relation
**Δr=d sinθ Bright: d sinθ=nλ Dark: d sinθ=(n+½)λ**
Exam preparation
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Review the key facts, formulas and checks before you move on.Young's Double-Slit Experiment
Sticky Notes · Quick Revision
Two slits:
- separation → `d`
- screen distance → `D`
- wavelength → `λ`
- Bright → `nλ`
- Dark → `(n+½)λ`
60-second revision
- YDSE produces alternating interference fringes.
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