Polycopiated : Geometric and physical optics courses and exercises : For students of 2nd LMD physics speciality and 1rt Mater physics of material speciality
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Date
2025
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Faculty of Sciences
Abstract
There is rectilinear propagation of light in a homogeneous medium. Propagation in a heterogeneous
medium leads to spatial fluctuations if the heterogeneity is not regular. The phenomenon is easily
observed above a flame: we see the objects located behind the flame. The observed spatio-temporal
fluctuations are due in this case to an irregular and rapidly variable distribution of the air index, which is
the seat of strong turbulence. Turbulence plays a particularly important and harmful role in astronomical
observation instruments where it is accentuated by the magnifications of the apparatus. Even slight
differences in the telescope tube (and in the atmosphere) can significantly alter the quality of images.
We will then assume that the path of different light rays passing through an optical instrument are
independent: this is the hypothesis of the independence of the light rays