light in a different light from cavemen to newton
TRANSCRIPT
Light in a different lightFrom cavemen to Newton
This seminar series
1. From cavemen to Newton: earliest ideas about light2. Particles and Waves: what is wave-particle duality?3. Blue Skies, Rainbows and Thunder Storms: the optics of weather4. The Optics of Vision: how the eye really works5. Optical Microscopy: seeing the micro-cosmos with one’s own eyes6. Star Wars Optics: the truth about lasers7. Fast Light, Slow Light: how materials influence the propagation of light8. Light Bits: CDs, optical fibers and telecommunication
9. Ultrafast Light: seeing molecules move with flashes of light.
http://eee.uci.edu/06f/87568
Eric Potma
Natural Sciences II, room 1107
Elusive messengers
Light allows us to see objects, but can we see light itself?
Light in Egypt
Light is the sight of God
Leucippus
Eidolon
How does eidolon stay intact?
How can big eidola fit through eye’s aperture?
Why can’t we see eidola in the dark?
Why can we see only front surfaces of objects?
Empedocles
Why can’t we see in the dark?
How fast are the ‘visual rays’?
How can the ray be wide and narrow simultaneously?
Plato’s fireAnd of the organs they first contrived the eyes to give light, and the principle according to which they were inserted is as follows. So much of fire as would not burn, but gave gentle light, they formed into a substance akin to the light of everyday life, and the pure fire which is within us and related to it they made to flow through the eyes in a stream smooth and dense, compressing the whole eye and specially the center part, so that it kept out everything of a coarser nature and allowed to pass only its pure element.
The shaft of rays from our eyes is a shaft of light. It can be pulled in when we focus on what is near our eyes and sent forth when we fix on objects that are at a distance, but when it is pulled in, it does not altogeter stop seeing distant objects, although of course, it sees them more obsurely the when it fixes its gaze upon them.
8 centuries after Plato:
Euclidian raysLines drawn from the eye pass through space of great extent
Form of space included within our vision is a cone, with its apex in the eye and its base at the limits of our vision
Those things on which vision falls are seen, and those things upon which vision does not fall are not seen
Things seen within a larger angle appear larger, things seen with a smaller angle appear smaller
Euclidian rays
A
B
C
Euclidian rays
A
B
C
D
Diocles’ rays
Archimedes’ mirror
Hero’s rays
A B
A B
Ptomely
End of visual rays
“There is no vision unless something comes from the visible object to the eye, whether of not anything goes out”
camera obscura
Light and eyes
Lenses to help the eye
Lenses to help the eye
Lenses to help the eye
Lenses to help the eye
Lenses to help the eye
Lenses to help the eye