Early Observations • And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness. - Genesis 1:3-4 • And God said, This is the token of the covenant which I make between me and you and every living creature that is with you, for perpetual generations: I do set my bow in the cloud, and it shall be for a token of a covenant between me and the earth. - Genesis 9:12-13
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Early Observations And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness.
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Early Observations
• And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness. - Genesis 1:3-4
• And God said, This is the token of the covenant which I make between me and you and every living creature that is with you, for perpetual generations: I do set my bow in the cloud, and it shall be for a token of a covenant between me and the earth. - Genesis 9:12-13
Early Observations
• Early lens dicovered in ruins of Nineveh believed to be 4000 years old
• Empedocles (500 BC)– Light has motion and travels at a fixed speed
• Aristotle (332 BC)– Pure light changed into colors by contamination
• Egyptians (200 AD)– Light travels from eye to illuminate object
• Alhazen (965 AD)– Light comes from sun or other objects– Made curved mirrors and pinhole camera obscura
Early Observations• Leonardo da Vinci
– Studied the ''Artificial Rainbow'' obtained by passing pure light through a prism
• Galileo (1600)– Tried to measure speed of light– Used lanterns separated by increasing distances– No valuable estimate
• Olaus Roemer (1675)– Used eclipses of Jupiter's satellites– Obtained a speed of 140,000 miles per second– Ridiculed by the French Academy of Sciences:
''It is absolutely impossible for anything, unless by the spirit of God, to attain such a speed''
Early Observations
• Newton– Studied chromatic aberration in lenses– Studied light passing through prisms
• Selected the brightest seven: Red, Orange, Yellow, Green, Blue, Indigo, and Violet– These are arbitrary
• Thought light was comprised of corpuscles– Unable to completely explain color
• Nature and Nature's Law lay hid at night. God said, 'Let Newton be,' and all was light.
Early Observations
• Christian Huygens– Published the wave theory of light in 1690– Could easily explain refraction– Hard to explain light traveling in a vacuum– Light carried on ''ether''
• Thomas Young (1801)– Double slit experiment– Determined wavelength of red light of 750 nm
• Augustin Jean Fresnel (1816)– Created diffraction gratings
Early Observations
• Sir William Herschel (1799)– Using a prism and a thermometer discovered
infrared radiation– Showed it behaves like visible light
• Johann Wilhelm Ritter– Used silver chloride to detect ultraviolet light
• James Clerk Maxwell (1864)– Theorized radiation beyond infrared– Produced and identified in 1887 by Heirich Hertz
Early Observations
• Jean Bernard Leon Focault (1850)– Used a rotaing mirror system– Obtained a speed of 187,000 miles/sec
• Albert Abraham Michelson (1879)– Obtained a speed of 186,284 miles/sec
• Current Speed is 186,284 miles/sec
Röntgen discovers x-rays
• Röntgen– Discovery
November 8, 1895– Public announcement
December 28, 1895– Public demonstration January
13, 1896• Worldwide acclaim in early
1896• Awarded first Nobel Prize in
Physics, 1901
Dual Nature of Light
• Max Planck (1901)– Radiation has a wave form– Made of small units of energy, called a quanta– Unified earlier theories
• On Monday, Wednesday, and FridayWaves boasted, ''It's my day,'‘On Tuesdays, Thursdays, and SaturdayParticles sang, ''Due it my way.'‘Sundays, though, were the very bestThe good Lord said, ''It's a day of rest.''
Electromagnetic Radiation
Albion College
Eye
• Every organism is light sensitive– Plants– Insects
• Complex eye• Simple brain
– Vertebrates• Simple eye• Complex brain
Eyes
• Sensory without contact• Optical Instrument– Described by Descartes