1
Fizeau’s Method
•
d
is the distance
between the wheel and
the mirror
⊗
t
is the time for one
round trip
• Then
c
= 2
d
/
⊗
t
•
Fizeau found a value
of
c
= 3.1 x 10
8
m/s
The Ray Approximation in
Geometric Optics
•
Geometric optics
involves the study of the
propagation of light
•
It uses the assumption that light travels in a
straightline path in a uniform medium and
changes its direction when it meets the surface of
a different medium or if the optical properties of
the medium are nonuniform
• The
ray approximation
is used to represent beams
of light
Ray Approximation
•
The rays are straight
lines perpendicular to
the wave fronts
•
With the ray
approximation, we
assume that a wave
moving through a
medium travels in a
straight line in the
direction of its rays
Ray Approximation, cont.
•
If a wave meets a
barrier, we will
assume that
λ
<<
d
–
d
is the diameter of the
opening
•
This approximation is
good for the study of
mirrors, lenses,
prisms, etc.
Reflection of Light
•
A ray of light, the
incident ray
, travels in a
medium
• When it encounters a boundary with a
When it encounters a boundary with a
second medium, part of the incident ray is
reflected
back into the first medium
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 Spring '09
 Total internal reflection, Specular reflection, Geometrical optics, ray approximation

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