Light in a different light

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Light in a different light

From cavemen to Newton

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This seminar series

1. From cavemen to Newton: earliest ideas about light

2. Particles and Waves: what is wave-particle duality?

3. Blue Skies, Rainbows and Thunder Storms: the optics of weather

4. The Optics of Vision: how the eye really works

5. Optical Microscopy: seeing the micro-cosmos with one’s own eyes

6. Star Wars Optics: the truth about lasers

7. Fast Light, Slow Light: how materials influence the propagation of light

8. Light Bits: CDs, optical fibers and telecommunication

9. Ultrafast Light: seeing molecules move with flashes of light.

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Slide 4

Elusive messengers

Light allows us to see objects, but can we see light itself?

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Light in Egypt

Light is the sight of God

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Leucippus

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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?

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Empedocles

Why can’t we see in the dark?

How fast are the ‘visual rays’?

How can the ray be wide and narrow simultaneously?

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Plato’s fire

And 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.

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Euclidian rays

Lines 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