Disclosing hidden messages in a dim Star Light

Geometrical Optics and Physical Optics

Lenses were used in Roman times and Seneca described the magnifying power of a ball of crystal, but spectacles were invented much later, in 1290, by friar Alessandro Della Spina in Pisa. Moreover, only in 1608 the German spectacle maker Hans Lippershey in Holland tried to patent a telescope, possibly invented by someone else. Paolo Sarpi received a report on it; then his friend Galileo converted the news of a Dutch toy into a new scientific instrument capable of 30 magnifications. He made a series of amazing discoveries that he reported in Sidereus Nuncius.

Lenses receiving light from left and right.
Principle of the astronomical telescope
Calculating the angular magnification of the telescope
  • At this point the only way to solve the problem is by following the famous statement by Roger Bacon: Natura non nisi parendo vincitur (The only way we can win over Nature is to obey its laws). Since light waves disobey Geometrical Optics, we must attain higher resolution by using the properties of light waves, that is, Physical Optics..

The main idea of astronomy using waves , in short

Physicists and astronomers have found a different road to progress, which exploits in various nontrivial ways the knowledge of Physical Optics, that is, the science of light waves. A plane wave having wave length is characterized by a wave vector directed along the direction of propagation and having modulus

The Young experiment and light waves

Young experiment for normal incidence
Young experiment for off-normal incidence
Diffraction with two incoherent plane waves
Minimum V is attained for a proper spacing of the slits
Figure 8: Albert Michelson (Wikipedia)
Figure 9 The Michelson interferometer (from Wikipedia)

Amplitude interferometry

Hanbury Brown and Twiss Effect

Figure 10 Scheme of the Hanbury Brown and Twiss effect


[1] M.Born and E. Wolf, Principles of Optics, Pergamon Press



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Michele Cini

Michele Cini


Retired Full Professor, Tor Vergata University. Quantum Theory of Transport, Pumping, Magnetism, Superconductivity, Non linear Optics, Electron Spectroscopy,..