What you’ll learn11 learning objectivesChoose one objective for a focused lesson, or study the complete topic.—C.3.1—Wavefronts and rays• Waves travelling in two and three dimensions can be described through the concepts of wavefronts and rays.Syllabus objective—C.3.2—Snell’s law• Snell’s law: n1 sinθ1 = n2 sinθ2.Syllabus objective—C.3.3—Refractive index• Refractive index: n=c/v.Syllabus objective—C.3.4—Total internal reflection• Total internal reflection condition uses critical angle: sinθc=n2/n1.Syllabus objective—C.3.5—Superposition• Superposition adds displacements where waves overlap.Syllabus objective—C.3.6—Coherence• Coherence requires constant phase difference between waves.Syllabus objective—C.3.7—Path difference• Path difference determines constructive or destructive interference.Syllabus objective—C.3.8—Two-source interference• Two-source interference depends on path difference and wavelength.Syllabus objective—C.3.9—Young double-slit equation• Young double-slit spacing: s = λD/d.Syllabus objective—C.3.10—Thin-film interference• Thin-film interference arises from reflected waves and phase changes.Syllabus objective—C.3.11—Resolution and Rayleigh criterion• Resolution is limited by diffraction; Rayleigh criterion sets resolvability.Syllabus objective