Abstract
This book was written for ophthalmologists and light will be one of our main topics. We assume that all of us – the authors and the readers alike – marvel about all the various ways that light appears. When we see the pole star in the night sky − because the process of doing it is apparently so self-evident − we are hardly aware that, through this viewing, we are participating in a fantastic process. The light left the star's hot atmosphere in Newton's time and was then underway, solitarily, through almost empty space until it entered our atmosphere and then passed almost unimpeded through several billion molecular shells. Finally, focused on the retina by the cornea and lens, it triggered a state change in rhodopsin molecules that, via a chain of chemical amplifications, led to the hyperpolarization of photoreceptors and fed electrical signals into the brain's neural network. At the end of the process stands the mystery of how the signal then arrives in conscious awareness.
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Notes
- 1.
Leonhard Euler (1707–1783), Swiss mathematician. Early in his life, he lost his vision in one eye and, at the time that he wrote the 200 tutorial letters to the princess of Anhalt-Dessau, he was almost totally blind in the other eye due to a cataract. Nevertheless, he continued his immensely creative work. Letters to a Princess of Germany (3 Vols., 1768–72).
- 2.
Based on the quantum theory of light developed between 1930 and 1960. The interested reader may find a discussion of the matter in Sect. 1.4.
- 3.
1 electron volt (1 eV) is the energy necessary to move an electron with its electrical charge (1e = 1.6∙10−19 Cb, Coulomb) over a voltage difference of 1 V (Volt). 1 eV = 1.6∙10−19 J (Joule). See Appendix for the relations between physical units.
- 4.
Thomas Young (1773–1829), British physician. Originator of the wave theory of light and the three-color theory of vision. He also explained ocular astigmatism.
- 5.
Young did not carry out his experiment with two openings but split a sun ray with a piece of paper.
- 6.
James Maxwell (1831–1879), Scottish physicist and mathematician. Creator of the fundamental equations of electrodynamics that are still exactly the same today. In a lecture, with three projectors, he demonstrated additive color mixing.
- 7.
Michael Faraday (1791–1867), English chemist and physicist, investigator of the fundamentals of electricity and electromagnetic fields.
- 8.
His laws convey, in mathematically exact form, the fact that electric charges and changing magnetic fields create electric fields – electric currents and changing electric fields are sources of magnetic fields. Maxwell’s equations are still valid today and are unchanged; they have even survived the “storm” of the special theory of relativity.
- 9.
Taylor GI (1909) Interference fringes with feeble light. Proc. Cambridge Phil. Soc 15:114.
- 10.
Mentioned in Sect. 1.2.
- 11.
In Marcel G. J. Minnaert’s very beautiful book Light and Color in the Outdoors, one finds information on how one can perceive “Haidinger’s brush” – as the only weak influence of the polarization of light on our visual perception.
- 12.
Edwin Land (1909–1991), American inventor and industrialist. As a student, he discovered how to fabricate polarization filters from plastic.
- 13.
LASER: Acronym for Light Amplification by Stimulated Emission of Radiation.
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Flammer, J., Mozaffarieh, M., Bebie, H. (2013). What Is Light?. In: Basic Sciences in Ophthalmology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-32261-7_1
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DOI: https://doi.org/10.1007/978-3-642-32261-7_1
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