Further, if  l1 and l 2 denote the
wavelengths of light in medium 1 and medium 2, respectively and if the
distance BC is equal to l 1 then the distance AE will be equal to l 2 (because
if the crest from B has reached C in time t, then the crest from A should
have also reached E in time t ); thus,
1
1
2
2
BC
AE
v
v
λλ
=
=
or
1
2
1
2
v
v
λ
=λ
(10 7)
CHRISTIAAN HUYGENS (1629 – 1695)
Christiaan Huygens
(1629 – 1695) Dutch
physicist, astronomer,
mathematician and the
founder of the wave
theory of light His book,
Treatise on light, makes
fascinating reading even
today He brilliantly
explained the double
refraction shown by the
mineral calcite in this
work in addition to
reflection and refraction