Template:POTD/2009-09-23
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2009 September
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Picture of the day
Wavefronts
from a
point source
in the context of
Snell's law
, which describes the relationship between the
angles of incidence
and
refraction
, when referring to
light
or other
waves
, passing through a boundary between two different
isotropic
media
, such as
water
and
glass
. The region below the gray line has a higher
index of refraction
and proportionally lower
wave velocity
than the region above it. The dotted red line is perpendicular to the wavefronts and thus represents a
Fermat-shortest path
from the source to a point in the lower medium.
Image credit:
Oleg Alexandrov
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