Example image of eyePlorer eyePlorer map for 'Snell's law': Angle of incidence Formula Isotropy Optical medium Optics Physics Refraction Wave Trigonometric functions Ray tracing (physics) Refractive index Fermat's principle Pierre de Fermat Velocity Willebrord Snellius Ptolemy Thebaid Confirmation bias Baghdad Ibn Sahl Aspheric lens Thomas Harriot Discourse on the Method René Descartes French language Christiaan Huygens Huygens–Fresnel principle Glass Anisotropy Birefringence Crystal Total internal reflection Derivative Optical path length Stationary point Drowning Boundary value problem Electromagnetic radiation Maxwell's equations Fresnel equations Square root Evanescent wave Exponential decay Rainbow Chromatic aberration Achromatic lens Refracting telescope Brachistochrone curve Wolfram Demonstrations Project Seismic refraction