Physics · Ch 6 — Optics
Wave Optics
Wave Optics
Wave optics studies the wave characteristics of light -- specifically the phenomena of interference, diffraction and polarisation, covered in the remaining sections of this chapter. Even the familiar ray-optics laws of reflection and refraction can be, and are, proved rigorously using wave optics (via Huygens' principle, in the next two subsections). Though light propagates as a wave, its direction of propagation continues to be conveniently represented as a ray, exactly as in ray optics. An everyday mechanical analogy for wave propagation is the spreading of circular ripples on the surface of still water after a stone is dropped in: every point on one ripple is at the same distance from the centre and hence in the same phase of up-and-down oscillation, making each ripple a physical example of a wavefront …
What this figure shows. Panel (a) shows circular ripples spreading outward on the surface of still water from the point where a stone was dropped; every point on any one ripple is at the same distance from the centre and is therefore in the same phase of up-and-down oscillation, so each ripple is a physical example of a wavefront. Panel (b) makes the general rule explicit: a wavefront (the locus of points in the same phase) is always drawn perpendicular to the ray, which points in the actual dir …