optics, waves and electromagnetic radiation
DESCRIPTION
OPTICS, WAVES AND ELECTROMAGNETIC RADIATION. Time Line of Ancient Philosophy as it Relates to the Origins of Science. Reflection and Refraction. Both properties of light obey rectilinear, geometric laws. Lenses and Refraction. Biconvex lens. Biconcave lens. - PowerPoint PPT PresentationTRANSCRIPT
OPTICS, WAVES AND ELECTROMAGNETIC RADIATION
• Ancient Philosophy and Light– Laws of Reflection and Refraction– Theories of Vision
• Rome and Decline of Natural Philosophy• Arab Natural Philosophy and its Rebirth in the West• Light: Particle or Wave
– Types of Waves– Interference and Resonance
• Discovery of the EM Spectrum• Demise of the Ether
Time line of Ancient Philosophy as it relates to the origins of science
Reflection and Refraction
Both properties of light obey rectilinear, geometric laws
Lenses and Refraction
Biconcave lens
Biconvex lens
Emission & Intromission Theories of Vision
Emission• Vision is sensation from rays
emitted by the eye• Multiple points• Thus, vision is external to
the eye• Earliest Proponents:
– Pythagoras?– Plato– Euclid– Ptolemy
Intromission• Vision is from physical forms
entering the eye• Single object• Vision occurs within the eye• Earliest Proponents:
– Aristotle– Galen
Arabic Natural Philosophy
Abu Ali al-Hasan ibn al-Hasan ibn al-Haythamالهي بن الحسن بن الحسن علي، أبو
Alhazen, 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
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 Albertus Magnus (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 Deux Veritas; intromission vision theory adopted
In the transition, there was a discussion about the relationship between material theories of light and vision.
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.
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)
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
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
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
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
Observation of Grimaldi best explained if light is a wave
Types of Waves
Transverse wave
Longitudinal wave
Constructive and destructive interference
Constructive Destructive
Resonance
One-slit Experiment
Double-slit Experiment and Interference
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
C= Wavelength(meters)*Frequency (Hz)C= 300,000 km/sec
Radio
Gugliemo Marconi1874-1937, Italy
Alexander Stepanovich Popov1859-1906, Russia
Michelson-Morley Experiment (1887)
Albert Abraham Michelson1852-1931, Prussia (now Poland) and USA1st American to win Nobel (1907)
Edward Willliams Morley1838-1923, USA
Doppler Effect
Christian Andreas Doppler1803-1853, Austria
• Suggested color relative to velocity (to explain color differences in binary stars)
• Concept applied also to sound