In a double-slit experiment, d=0.25 cm, D=100 cm, λ=6000 Å, and I₀ is the central-maximum intensity. Find the intensity at x=4×10⁻⁵ m from the central maximum.
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In a double-slit experiment, d=0.25 cm, D=100 cm, λ=6000 Å, and I₀ is the central-maximum intensity. Find the intensity at x=4×10⁻⁵ m from the central maximum.

G1 Physics · Accepted Answer

Fringe width β=λD/d=(6000×10⁻¹⁰×1)/(0.25×10⁻²)=2.4×10⁻⁴ m. Here x/β=(4×10⁻⁵)/(2.4×10⁻⁴)=1/6, so φ=2π/6=π/3. Therefore I/I₀=cos²(φ/2)=cos²(π/6)=3/4. Hence I=3I₀/4.