Transcript What is the light?

ARCHIMEDES’ S BURNING
GLASSES
AND THE LIGHT
ARCHMIDES OF SYRACUSE
Archimedes of Syracuse (Syracuse, 287 b.C. – Syracuse, 212 b.C.),
a mathematician, an engineer, a physicist and an ancient Greek
inventor (Siceliot), was one of the greatest scientists of history.
Syracuse
ARCHIMEDES’S BURNING GLASSES
In collective consciousness, the
burning glasses are indissolubly
linked to the siege of Syracuse,
during which Archimedes had used
them in order to burn the Roman
ships.
The legend narrates that in 216 B.C.,
when Archimedes was more than 70
years old, Gerone, the tyrant of the
city, died. Siracusa allied with the
Carthaginians and was, therefore,
sieged by the Roman army, leaded by
the consul Claudio Marcello.
THE LIGHT
• What is the light?
• How does it propagate?
• How was it considered during the
centuries?
To explain the light and the various luminous
phenomena during the centuries, three different
theories were affirmed:
• The Geometric Optics
• The Wave Theory
• The Quantum Theory
THE GEOMETRIC OPTICS
This theory was developed above all thanks to the studies of two
physicians.
Cristiaan Huygens
Isaac Newton
Reflection
• The incidence ray, the reflected ray and the perpendicular line
belong to the same plane.
•The incidence angle is isometric to the reflection angle.
Refraction
•The incidence ray, the refracted ray and the perpendicular line
belong to the same plane.
•The ratio between the sine of the incidence angle and the sine of
the refracted angle is constant.
Total Refraction and Reflection
= n 12
THE OPTICAL PRISM
The optical prism is a refracting means limited by
two not parallel plane facets
The light is composed by a spectrum of different chromatic
components; they are diverted by the optical prism because of
their different degree of refrangibility.
This allows the light dispersion.
The human eye perceives only the following colours:
Through the phenomenon of refraction
it is explained why the rainbow happens
The rainbow is a luminous arch in which we can observe
the decomposition of light visible in its spectre.
Such a decomposition takes place for the refraction of the luminous
ray inside the little water drops scattered in the atmosphere
We can distinguish two types of rainbow:
Primary: a reflection
.
Secondary: double reflection
In1800 Maxwell explains the light as an electromagnetic
phenomenon, that is simultaneous propagation of
an electrical and magnetic signal.
The light travels at the same speed as the electromagnetic waves, in
vacuum similar to about 3*10^8 m/sec. As the electromagnetic
waves, the light is a diagonal and not lingitudinal wave.
THE LIGHT IN THE WAVE THEORY
The Electromagnetic Field
EINSTEIN’S
CONTRIBUTION
• The light speed in vacuum is always the
same, for any observer. It is independent
from the source motion and from the
observer. It is a universal constant.
• The physical laws that describe the natural
phenomena have the same form for all the
inertial systems.
The Physicist…
“Enters in an intimate contact with Mother Nature
in order to understand her laws, reveal her secrets,
solve situations and create wellness”
From Archimedes to nowadays
history keeps happening!
The End
Power Point realised by Teacher Randazzo Tullio
English Translation by Teacher Aglio Valentina