Key Concepts: Diffraction & Interference

Diffraction

• The bending and spreading of waves around obstacles or through openings.
• Most significant when the opening/obstacle size is comparable to the wavelength.
• Single-slit diffraction produces a central bright maximum with weaker secondary maxima.

Double-Slit Interference (Young's Experiment)

• Two coherent sources produce an interference pattern of bright and dark fringes.
• Bright fringes: d sin θ = nλ (constructive, n = 0, 1, 2, ...).
• Dark fringes: d sin θ = (n + ½)λ (destructive).
• Fringe spacing: Δy = λL/d.

Diffraction Gratings

• Many parallel slits produce very sharp, bright maxima at d sin θ = nλ.
• Used in spectrometers to separate light into its component wavelengths.