Chapter 36: Diffraction

Single-slit diffraction demonstrates how narrow openings spread light into characteristic patterns with a bright central maximum flanked by dimmer secondary maxima, where dark fringes occur according to the relationship a sin θ = mλ, and the intensity distribution follows the sinc-squared function. Multiple-slit arrangements produce sharper interference maxima governed by d sin θ = mλ, with the number of slits determining the quantity of minima and secondary maxima between principal peaks. Diffraction gratings containing thousands of parallel slits create extremely sharp spectral lines that separate white light into constituent wavelengths, with chromatic resolving power dependent on both the number of illuminated slits and diffraction order. X-ray diffraction utilizes Bragg's law (2d sin θ = mλ) to analyze crystal structures by measuring constructive interference from atomic planes, providing crucial insights into material properties and molecular arrangements. Circular apertures generate Airy disk patterns with concentric rings, where the angular size of the central disk determines optical resolution limits according to Rayleigh's criterion. The chapter concludes with holography principles, explaining how coherent laser light creates interference patterns between object and reference beams to record both amplitude and phase information, enabling three-dimensional image reconstruction through virtual and real image formation.