9 Optical Properties
Transcript of 9 Optical Properties
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OPTICAL PROPERTIES
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OPTICAL PROPERTY a materials response to exposure to electromagnetic
radiation and, in particular, to visible light
Electromagneticradiation
energy radiated in theform of a wave consistingof electric and magneticfield components that are
perpendicular to eachother and also to thedirection of propagation
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Electromagnetic spectrum spans the wide range from -rays through radiowaves
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Electromagnetic Spectrum
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Speed of light in vacuum:
c = 3 x 108
m/s
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LIGHT INTERACTIONS WITH SOLIDS
When light proceeds from one medium into
another, the following may happen:
.
2. Refraction
3. Transmission
4. Absorption
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REFLECTIONLaw of Reflection
The incident ray, the reflected ray, and the normal tothe surface all lie in the same plane, and the angle of
reflection r equals the angle of incidence i.
r = i
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2 Types of Reflection1. Specular Reflection when
parallel light rays strike a smooth,
plane surface, the reflected raysare parallel to each other.
Reflections on still water are anexample of specular reflection.
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Diffuse Reflection when parallel lightrays strike an irregular surface, the
reflected rays are in various directions
The image blurs when thewater is rough.
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REFRACTION bending oflight due to change invelocity
Index of refraction:
n = c v
where c = speed of light in vacuum
v = speed of light in a mediumvacuum: n = 1
air: n 1
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Indices of Refraction for some materials
Substance n
Glass 1.523
Polycarbonate 1.584
a .
Diamond 2.419
Ice 1.309
Water 1.33
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Snells Law of Refraction
When light travels from a material with refractive index n1 into amaterial with refractive index n2, the refracted ray, the incident ray,and the normal to the surface all lie in the same plane. The angle of
refraction 2 is related to the angle of incidence 1 by
n1sin1 = n2sin2
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Transparent materials that are capable oftransmitting light with relatively littleabsorption and reflection
Translucent materials through which light
, ,scattered within the interior
Opaque materials that are impervious tothe transmission of visible light
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Problems1. A beam of light is traveling in air and strikes a
material. The angles of incidence and refraction
are 63 and 21.6, respectively. (a) What is theangle of reflection? (b) What is the index ofrefraction of the material? (c) What is thematerial?
2. Using a laser and electronic timing device, youfind that light travels 2.5 m within a plastic rodin 11.5 x 10-9 s. What is the index of refractionof the plastic?
3. What is the speed of light in diamond, glassand water?