Transcript KS4 Waves: Total Internal Reflection and Communication

KS4 Waves: Total Internal Reflection
and Communication
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Total Internal Reflection
Angle r
Angle i
Refracted
ray
Angle r
Refraction or
Reflection?
15
30
45
Angle r
Angle i
Incident
ray
Reflected
ray
60
75
At what angle of incidence did the ray change from
refraction to reflection? It depends upon the material you used.
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Simulation of a ray of light passing through
a semi-circular glass block
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Total Internal Reflection
This angle is called the critical angle [ c]
i<c
i=c
Refraction
Critical case
i>c
Total Internal
Different materials have different critical angles. Reflection
Diamond has the lowest at 24º which is why it
[TIR]
reflects so much light.
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The Critical Angle
How does refractive index affect the critical angle?
Research the missing values below and then
make a conclusion…
Material
Refractive
index
Critical
angle
Glass
1.5
42°
Water
1.33
49°
Diamond
2.4
24°
The greater the refractive index the smaller the
critical angle.
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Total Internal Reflection
Optical
Whatfibres,
are the
that are used in
communication,
applications ofuse
total
total
internal
internal
reflection.
reflection?
You
could
asked
A beam
ofbe
light
to
drawthe
on optical
the path
enters
of
the beam in an
fibre….
exam.
…NOTE how it is
refracted as it
enters the fibre…
…it travels down the
fibre through repeated
total internal reflections.
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Optical versus electrical
Research why communications systems now use
optical fibres instead of copper wires, use the table
below to help you.
Optical
Electrical
Information
Carry more
Attenuation
Less
More
Interference
No
Yes
Cost
More
Less
How is attenuation
solved in optical and
electrical fibres?
Carry less
Regenerators for electrical cables
Repeaters for optical fibres
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Which of the following is not a use of total
internal reflection?
A. Periscopes
B. Endoscopes
C. Fibre optic communication
D. Mirrors

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