Reflection ( 反射 ) incident rayreflected ray plane mirror angle of incidence angle of reflection...
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Transcript of Reflection ( 反射 ) incident rayreflected ray plane mirror angle of incidence angle of reflection...
Reflection (Reflection ( 反射反射 ))
incident ray reflected ray
plane mirror
angle of incidence
angle of reflection
normalReflection of Light (Reflection of Light ( 光的反射光的反射 ))
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Incident Rays
(入射線 )
The light ray moving towards the mirror
Reflected Rays
(反射線 )
The light ray moving out of the mirror
Normal
(法線 )
The line perpendicular (垂直 ) to the mirror
Angle of incidence
(入射角 )
The angle between the incident ray and the normal.
Angle of reflection
(反射角 )
The angle between the reflected rays and the normal.
incidentray
reflectedray
Laws of reflection:
The angle of
reflection r
equal to
of incidence i.
plane mirror
i r
1.
is
the angle
normalvertical plane
Laws of reflectionLaws of reflection ((反射定律反射定律 ))
i = r
Laws of reflection:
The incident ray,
the reflected ray
and the normal
all lie in the sameplane.
incidentray
reflectedray
normal
plane mirror
vertical plane2.
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i = 0 r = 0 air
mirror
When the angle of incidence equals to zero (i = 0) , the angle of reflection is also zero (r = 0).
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40°
40°
60°
60°
30°
30°
45°
45°
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5.3 Experiment (實驗 )
電源
光箱
量角器
平面鏡
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i / 0 30 45 60 75
r /
Conclusion (結論 )
The angle of incidence is ____________ the angle of reflection.
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i / 0 30 45 60 75
r / 0 30 45 60 75
Conclusion (結論 )
The angle of incidence is _equal to_ the angle of reflection.
Will the reflected rays remain parallel (平行 ) after reflection?
Regular reflection Regular reflection ((單向反射單向反射 ))
same i same r The reflected rays are therefore parallel.
i i ir r r
parallel incident rays parallel reflected rays
plane mirror
Each light ray obeys the laws of reflection.
For flat ( 平 ) and smooth ( 滑 ) surface,
plane mirror
Regular reflection (單向反射 ) occurs at:
The following reflecting surfaces can form clear images due to regular reflection.
a calm water surfacemetal surface
For rough (粗糙 ) surface,
i1i2
i3
r1 r2
r3
rough surface
parallel incident rays
reflected rays are not parallel
Each light ray obeys the laws of reflection.different i different r
Diffuse reflectionDiffuse reflection ((漫反射漫反射 ))
Diffuse reflection occurs at a rough surface (e.g. a piece of paper).
e.g. a piece of paper
Lateral inversion (Lateral inversion ( 橫向倒置橫向倒置 ))
Mirror images are laterally inverted.
The laterally inverted words on an ambulance (救護車 )
the object image formed by the plane mirror
An image formed by a plane mirror is
1. same size as the object,
2. laterally inverted. ((橫向倒置橫向倒置 ))
3. same distance
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Uses of plane mirrors (平面鏡的應用 )
rear-view mirrors (倒後鏡 )
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Explain why the Chinese characters 救護車 are printed in the special way as shown.
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So that the driver of the car in front of the ambulance can see the Chinese characters 救護車 without lateral inversion.
PeriscopePeriscope ((潛望鏡潛望鏡 ))
A periscope consists of two mirrors The mirrors make an angle of 45 with the
line joining them.
Periscopes are used in a double-deckers (雙層巴士 )
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Periscope (潛望鏡 ) used in submarine (潛水艇 ).
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Plane mirrors used in interior design (室內設計 ).
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Plane mirror used by dentist (牙醫 ).
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In Figure 5.4, draw ONE light ray from the head of the object to the eye after reflection from the two mirrors.
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Homework: Assignment Book 1. Chapter 5 Q.1 – Q.8 (p.7-9)
2. Deadline: