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350
YEARS
OF
SCIENCE
65
Christiaan Huygens soon looked into
the question of light beam reflection and
refraction.
θ
1
θ
2
=
θ
2
θ
1
REFLECTION
REFRACTION
1
θ
1
θ
2
θ
2
θ
1
=
1
Mirror
Incident ray
Normal to the point
of incidence Reflected ray Incident ray
Refracted ray
Normal to the point
of incidence
Index of medium n
2
Index of medium n
n
sin
2
n
sin
Air
Glass
© From Fabien2005/Wikipedia
Christiaan Huygens (1629-1695)
© gallica.bnf.fr - Bibliothèque nationale de France
© gallica.bnf.fr - Bibliothèque nationale de France
Huygens’ wave model, expressed in 1678 and described in full
in his Treatise on Light (1690), accounts for refraction provided
that the speed of light is slower in the denser medium than in air,
in contrast to Newton's corpuscular theory.
© gallica.bnf.fr - Bibliothèque nationale de France
© Morphart - Fotolia
through his law of universal gravitation. It took
more than one century before Thomas Young,
in England, and Augustin Fresnel, in France,
developed the wave model of light, as the only
one able to account for the phenomena of
interference and diffraction, that they carefully
studied in remarkable experiments.