Six Lectures On Light

Contents

• Preface to the fourth edition.

• Lecture I.

  Introduction -- Uses of Experiment -- Early Scientific Notions -- Sciences of Observation -- Knowledge of the Ancients regarding Light -- Defects of the Eye -- Our Instruments -- Rectilinear Propagation of Light -- Law of Incidence and Reflection -- Sterility of the Middle Ages -- Refraction -- Discovery of Snell -- Partial and Total Reflection -- Velocity of Light -- Roemer, Bradley, Foucault, and Fizeau -- Principle of Least Action -- Descartes and the Rainbow -- Newton's Experiments on the Composition of Solar Light -- His Mistake regarding Achromatism -- Synthesis of White Light -- Yellow and Blue Lights produce White by their Mixture -- Colors of Natural Bodies -- Absorption -- Mixture of Pigments contrasted with Mixture of Lights

• Lecture II.

  Origin of Physical Theories -- Scope of the Imagination -- Newton and the Emission Theory -- Verification of Physical Theories -- The Luminiferous Ether -- Wave-theory of Light -- Thomas Young -- Fresnel and Arago -- Conception of Wave-motion -- Interference of Waves -- Constitution of Sound-waves -- Analogies of Sound and Light -- Illustrations of Wave-motion -- Interference of Sound Waves -- Optical Illustrations -- Pitch and Color -- Lengths of the Waves of Light and Rates of Vibration of the Ether-particles -- Interference of Light -- Phenomena which first suggested the Undulatory Theory -- Boyle and Hooke -- The Colors of thin Plates -- The Soap-bubble -- Newton's Rings -- Theory of 'Fits' -- Its Explanation of the Rings -- Overthrow of the Theory -- Diffraction of Light -- Colors produced by Diffraction -- Colors of Mother-of-Pearl.

• Lecture III.

  Relation of Theories to Experience -- Origin of the Notion of the Attraction of Gravitation -- Notion of Polarity, how generated -- Atomic Polarity -- Structural Arrangements due to Polarity -- Architecture of Crystals considered as an Introduction to their Action upon Light -- Notion of Atomic Polarity applied to Crystalline Structure -- Experimental Illustrations -- Crystallization of Water -- Expansion by Heat and by Cold -- Deportment of Water considered and explained -- Bearings of Crystallization on Optical Phenomena -- Refraction -- Double Refraction -- Polarization -- Action of Tourmaline -- Character of the Beams emergent from Iceland Spar -- Polarization by ordinary Refraction and Reflection -- Depolarization.

• Lecture IV.

  Chromatic Phenomena produced by Crystals in Polarized Light -- The Nicol Prism -- Polarizer and Analyzer -- Action of Thick and Thin Plates of Selenite -- Colors dependent on Thickness -- Resolution of Polarized Beam into two others by the Selenite -- One of them more retarded than the other -- Recompounding of the two Systems of Waves by the Analyzer -- Interference thus rendered possible -- Consequent Production of Colors -- Action of Bodies mechanically strained or pressed -- Action of Sonorous Vibrations -- Action of Glass strained or pressed by Heat -- Circular Polarization -- Chromatic Phenomena produced by Quartz -- The Magnetization of Light -- Rings surrounding the Axes of Crystals -- Biaxal and Uniaxal Crystals -- Grasp of the Undulatory Theory -- The Color and Polarization of Sky-light -- Generation of Artificial Skies.

• Lecture V.

  Range of Vision not commensurate with Range of Radiation -- The Ultra-violet Rays -- Fluorescence -- The rendering of invisible Rays visible -- Vision not the only Sense appealed to by the Solar and Electric Beam -- Heat of Beam -- Combustion by Total Beam at the Foci of Mirrors and Lenses -- Combustion through Ice-lens -- Ignition of Diamond -- Search for the Rays here effective -- Sir William Herschel's Discovery of dark Solar Rays -- Invisible Rays the Basis of the Visible -- Detachment by a Ray-filter of the Invisible Rays from the Visible -- Combustion at Dark Foci -- Conversion of Heat-rays into Light-rays -- Calorescence -- Part played in Nature by Dark Rays -- Identity of Light and Radiant Heat -- Invisible Images -- Reflection, Refraction, Plane Polarization, Depolarization, Circular Polarization, Double Refraction, and Magnetization of Radiant Heat

• Lecture VI.

  Principles of Spectrum Analysis -- Prismatic Analysis of the Light of Incandescent Vapors -- Discontinuous Spectra -- Spectrum Bands proved by Bunsen and Kirchhoff to be characteristic of the Vapor -- Discovery of Rubidium, Cæsium, and Thallium -- Relation of Emission to Absorption -- The Lines of Fraunhofer -- Their Explanation by Kirchhoff -- Solar Chemistry involved in this Explanation -- Foucault's Experiment -- Principles of Absorption -- Analogy of Sound and Light -- Experimental Demonstration of this Analogy -- Recent Applications of the Spectroscope -- Summary and Conclusion

• Appendix

  On the Spectra of Polarized Light
  Measurement of the Waves of Light

• Index