OPTICS, WAVES AND ELECTROMAGNETIC RADIATION

1. OPTICS, WAVES AND ELECTROMAGNETIC RADIATION

2. Time Line of Ancient Philosophy as it Relates to the Origins of Science

3. Reflection and Refraction Both properties of light obey rectilinear, geometric laws

4. Lenses and Refraction Biconvex lens Biconcave lens

5. Emission & Intromission Theories of Vision Emission Intromission Vision is from physical forms entering the eye Single object Vision occurs within the eye Earliest Proponents: Aristotle Galen • Vision is sensation from rays emitted by the eye • Multiple points • Thus, vision is external to the eye • Earliest Proponents: • Pythagoras? • Plato • Euclid • Ptolemy

7. Arabic Natural Philosophy

8. Abu Ali al-Hasanibn al-Hasanibn al-Haytham أبو علي، الحسن بن الحسن بن الهيAlhazen, the Persian • Modified intromission theory to support multiple rays of Euclid and Ptolemy, but from the object • Used geometrical, optical, and anatomical arguments • Wrote 7-volume treatise on Optics based on his observations and experimental work • Proposed speed of light was finite 965 (Basra in present-day Iraq) – 1040 Cairo, Egypt

9. Rebirth of Philosophy in Western Europe • The fall of Islamic Empire in Spain • Capture of Toledo and its library (1085) • Translations of Greek texts from Arabic to Hebrew to Latin –much guided by AlbertusMagnus (1193/1206-1280; present-day Germany) • Greek philosophy, especially Aristotle, accommodated to church doctrine by Thomas Aquinas (1225-1274; present-day Italy). Natural philosopher with concept of DeuxVeritas; intromission vision theory adopted

10. In the transition, there was a discussion about the relationship between material theories of light and vision.

11. Kepler, vision, and light • Johannes Kepler (1571-1630), in the mathematical tradition of medieval perspectivists, and benefiting from the ocular anatomy presented by Felix Platter (1536-1614). • 'How an infinity of rays from each point in the visual field is drawn into a coherent, point-to-point correspondence in the eye.' Against tradition, Kepler argued that the crystalline lens re-focused intromitted rays on the retina where vision was made possible. Significantly, Kepler called this image a 'pictura.' • However, as Alhazan had shown, such a lens makes an upside-down picture.

12. Rene Descartes (1596-1650) • In his need to connect the observer with the observed (Cartesian dualism) • Tied the world we see with the mechanical body by means of tiny threads (not as pictures) • Interpret visual information by linguistic theory (we have an innate ability to interpret visual information)

13. Francesco Maria Grimaldi Noted diffraction of light (a term coined by Leonardo da Vinci), cannot be explained if light operates only by rectilinear laws. 1618-1663, present-day Italy

14. Optics of Isaac Newton • Light is corpuscular and obeys rectilinear laws • Newton proposed that light corpuscles propagate in a luminous ether • Light comes from a luminous source and reflects off of visible objects • White light is made of all colors

16. Christiaan Huygens • Light is a wave • Light has a finite speed • Defined light phenomena on the basis of wave fronts in the luminous ether • Invented projector • Invented pendulum clock • Many other contributions in physics and astronomy 1629-1695, The Dutch Republic

17. Thomas Young and wave theory of light • Physician • Interpreter of Rosetta Stone • Contributed to theories of vision, mechanics, energy, music, language, physiology • Interference experiments with light 1773-1829; Great Britain

18. Observation of Grimaldi best explained if light is a wave

19. Types of Waves Transverse wave Longitudinal wave

20. Constructive and destructive interference Destructive Constructive

21. Resonance

22. One-slit Experiment

23. Double-slit Experiment and Interference

24. Discovery of the EM Spectrum • Visible light: ROYGBV • 1800 (William Herschel) IR radiation detected by measuring temp of light split by prism; invisible light below red was warm • 1801 (John Ritter) calorific rays (UV) beyond violet caused photochemical reactions similar to those of violet • 1845 (Michael Faraday) polarized light altered by magnetic field; thus, light phenomena are electrical and magnetic • 1860-1870 (James Maxwell) set of equations that suggested a constant velocity of light and described wave patterns in a field • 1886 (Heinrich Hertz) used Maxwell’s equations to define undiscovered waves (now called radio waves and microwaves). He was able to focus and reflect these waves • 1895 (Wilhelm Röntgen) defined x-rays • 1900 (Paul Villard), 1910 (William Henry Bragg) gamma radiation

25. C= Wavelength(meters)*Frequency (Hz) C= 300,000 km/sec

26. Radio Gugliemo Marconi 1874-1937, Italy Alexander Stepanovich Popov 1859-1906, Russia

27. Michelson-Morley Experiment (1887) Edward Willliams Morley 1838-1923, USA Albert Abraham Michelson 1852-1931, Prussia (now Poland) and USA 1st American to win Nobel (1907)

28. Doppler Effect • Suggested color relative to velocity (to explain color differences in binary stars) • Concept applied also to sound Christian Andreas Doppler 1803-1853, Austria