ch.7 refraction index ( 折射率 ) 1 2 incident ray refracted ray angle of incidence angle of...
TRANSCRIPT
2
IncidentRay
RefractedRay
Angle ofincidence
Angle of Refraction
air
glass
Angle of reflection Reflected
Ray
Light travelling from air to glass
The light ray bends towards the normal. ( 偏向法線 )
refracted ray
incident ray
normal
angle of incidence
angle of refraction
air
glass
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glassglassairair
incident ray reflected ray normal
normal
折射線(refracted ray)
折射角 (angle of refraction) 折射角 (angle of refraction)
angle of incidence
angle of incidence
Law of refraction (折射定律 ) Law of refraction (折射定律 )
4r
i
sin
sin= n (refractive index)
Refractive index of some common materials
Material Refractive index
Air 1.00
Water 1.33
Alcohol (酒精 ) 1.36
Perspex (有機玻璃 ) 1.50
Glass 1.50 – 1.70
Diamond (鑽石 ) 2.42
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Refractive index (Refractive index ( 折射率折射率 ))
nX – refractive index ( 折射率 ) of medium X
normal
air
medium X
a
X
XX
a nθ
θ
sin
sin
6
8
Class Practice 7.1
55
60
air Xn = sin i / sin r = sin 60 ° / sin (90-55) ° = sin 60 ° / sin 35 °
= 1.51
Answer is C
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Class Practice 7.2
air
X
air
Y
air
Z
r
i
sin
sin= n (refractive index) r↓ means n↑
∵ rx > ry > rz n∴ x < ny < nz answer is C
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Class Practice 7.4 (a)
r
50air
water
sin 50° / sin r = 1.33
sin r = sin 50° / 1.33 = 0.576
∴ r = 35.2°
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Class Practice 7.4 (a)
i = 40 °
sin 40° / sin r = 1.33
sin r = sin 40° / 1.33 = 0.483
∴ r = 28.9°
r
50 airwater