ARCHIMEDES’ S BURNING GLASSES AND THE LIGHT

1. ARCHIMEDES’ S BURNING GLASSES AND THE LIGHT

2. 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

3. 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.

4. THE LIGHT • What is the light? • How does it propagate? • How was it considered during the centuries?

5. 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

6. THE GEOMETRIC OPTICS This theory was developed above all thanks to the studies of two physicians. Isaac Newton CristiaanHuygens

7. 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.

8. Total Refraction and Reflection n = 1 2

9. THE OPTICAL PRISM The optical prism is a refracting means limited by two not parallel plane facets

10. 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:

11. 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.

12. Such a decomposition takes place for the refraction of the luminous ray inside the little water drops scattered in the atmosphere We can distinguishtwotypes of rainbow: . Primary: a reflection Secondary: double reflection

13. 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.

14. THE LIGHT IN THE WAVE THEORY The Electromagnetic Field

15. 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.

16. 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!

17. The End Power Point realised by Teacher Randazzo Tullio English Translation by Teacher Aglio Valentina