Wave Optics: One-Page Formula Sheet

Wave Optics — formula sheet

Formulas

• Fringe width β = λD/d
• Intensity I = 4I₀ cos²(φ/2)
• Fringe shift = (μ − 1)tD/d
• Single slit minima: a sinθ = nλ; Malus: I = I₀ cos²θ

Key ideas

• Path difference nλ gives bright fringes; (n + ½)λ gives dark
• Fringe width depends on λ, D and d
• A thin film in one slit shifts the whole pattern
• Malus' law for polarised light

Traps to avoid

• Using the YDSE minima condition for single-slit diffraction
• Forgetting λ changes inside a medium (λ/μ)
• Wrong direction of fringe shift

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