Skip to content
Login Register

#first dark fringe

2 public questions tagged with this topic.

Wave Properties, Frequency and Energy Conservation

What is the distance of the first dark fringe from the central maximum in a double-slit experiment if \( \lambda = 650 \

**Wave model predicts** light bends away from normal when entering rarer medium because speed increases, Snell's law n₁ sinθ₁ = n₂ sinθ₂, n₁>n₂ so sinθ₂>sinθ₁ θ₂>θ₁ away from normal, towards normal when denser, wavefront slows in denser, Huygens construction shows bending. For the first dark fringe, x = ((n + (1/2)) λ D/d) , n = 0 . x = ((1/2) × 6.5 × 10⁻⁷ × 1.0/5.0 × 10⁻⁴) = 6.5 × 10⁻⁴ m = 0.65 mm . Using Δ = d sinθ, y = n λ D/d, a sinθ = n λ, I = I₀ cos²θ, n = c/v, sinC = 1/n, λ' =

Ref: NCERT > Physics Book > Wave Optics > Wave Properties, Frequency and Energy Conservation

View Details
Interference - Double-Slit and Coherence

What is the path difference for the first dark fringe in a double-slit experiment?

**Double-slit vs single-slit** double-slit interference pattern has equally spaced bright fringes with envelope due to single-slit diffraction, single-slit central maximum width 2λ D/a, intensity of secondary maxima decreases with order, condition for coherence constant frequency and phase, path difference for bright n λ, dark (n+½)λ. Destructive interference occurs at Δ = (n + (1/2))λ . For the first dark fringe, n = 0 , so Δ = (λ/2) . Using Δ = d sinθ, y = n λ D/d, a sinθ = n λ, I = I₀ cos²θ, n = c/v, sinC = 1/n, λ' = λ/n and A = 2a cos(φ/2), calculation gives (λ/2),

Ref: NCERT > Physics Book > Wave Optics > Interference - Double-Slit and Coherence

View Details