Slide 1
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A History of Light
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Slide 2
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Pythagoras‘ Particle' theory of light.
Pythagoras assumed that every visible object
emitted a stream of particles that are received by
the eye. Consequently Pythagoras reasoned that,
"light consists of rays that acting like feelers, travel
in straight lines from the eye to the object, and the
sensation of sight is obtained when these rays
touch the object“.
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Slide 3
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The Platonic School took the opposite approach
by supposing that vision was produced by rays of
light that originate in the eye and then strike the
object in view.
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Aristotle concluded that light travels in something
like waves. Proposing a relationship between color
and sound (music) he wrote: "colours may mutually
relate like musical concords for their pleasantest
arrangement like those concords mutually
proportionate".
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Slide 4
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EARLY OPTICS & LENSES - (c 300 BC)
The earliest known lenses to the Greeks and Romans
consisted of glass spheres filled with water
(burning lenses).
ARISTOTLE - (384 - 322 BC)
He was a pupil of Plato but had a different theory of light
from the Pythagorean School. Aristotle concluded that
light travels in something like waves.
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Slide 5
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EUCLID - (320 - 275 BC)
Euclid, a mathematician studied light and followed the
teachings of Plato. He described the behavior of light,
anticipated a ray theory for light, and was probably the
first to consider the speed of light.
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Euclid believed the speed of light must be very fast
because you can close your eyes and then, when you
reopen them even the distant stars appear instantly.
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Slide 6
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HERO OF ALEXANDRIA - (c 150 BC)
Probably born in Egypt he wrote at least 13 works on
the subjects of applied mathematics, mechanics and
physics. Although Euclid could explain plane surface
reflection Hero is often credited with discovering
the properties of reflection of light and formulating a
concise law of reflection.
PTOLEMY - (c 100 - c 170 AD)
Also at Alexandria, Ptolemy was also able to measure
the bending of a beam of light as it passed from air into
water or glass. He did not however formulate a law of
refraction.
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Slide 7
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ALHAZEN (IBN AL HAITAM) - (965 - 1039)
He was one of the earliest, to write and describe optical
theory. He studied light, the nature of vision, the eye, and
solar and lunar eclipses. His early experiments led to a
forerunner of the Camera Obscura which he used
to prove that light travels in straight lines. He also studied
reflection and refraction.
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Slide 8
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DA VINCI - (1452 - 1519)
There is evidence that Da Vinci may have combined
lenses (telescope) to observe the moon. Da Vinci’s
notes were kept secret during his lifetime and were
only edited after his death. It is not apparent that they
had any influence on Galileo who employed the
telescope in the early 1600's.
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Slide 9
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HUYGENS - (1629 - 1695)
Huygens believed light consisted of waves. His wave
theory suggested that light results from vibration in
luminous materials. Light was transmitted through the
aether as wavelike movements (waves on water).
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Slide 10
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NEWTON - (1642 - 1727)
Newton considered his work on optics to be experimental
philosophy. It was his intent to use direct observation and
avoid speculative hypotheses. Although his work showed
both wave and corpuscular properties for light he
embraced the corpuscular idea. Colour in Newton’s mind
was the result of corpuscles of light inciting vibrations in
the aether.
Nature and Nature's laws lay hid in Night:
God said, Let Newton be, and all was Light"
(Alexander Pope, 18th Century)
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Slide 11
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ROEMER - (1644 - 1710)
Measured the speed of light in 1676 using the moons of
Jupiter. He calculated the speed to be about
2.4 X 108 m/s.
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Slide 12
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Slide 13
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