Chapter 1 : INTRODUCTION TO OPTICS. Optics is the physical science which studies light and the laws...
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Transcript of Chapter 1 : INTRODUCTION TO OPTICS. Optics is the physical science which studies light and the laws...
OpticsOptics is the physical science which is the physical science which studies light and the laws of vision.studies light and the laws of vision.
1. Light phenomena1. Light phenomena
1.1. Natural and artificial light sources1.1. Natural and artificial light sources
IncandescenceIncandescence FluorescenceFluorescence PhosphorescencePhosphorescence
the sun, a fire, the sun, a fire, the metal wire the metal wire
filament of a filament of a conventional light conventional light
bulbbulb
Fluorescent tubeFluorescent tube the hands of a watch, the hands of a watch, the northern lightsthe northern lights
warm lightwarm light cold lightcold light cold lightcold light
Stops when the Stops when the stimulation stopsstimulation stops
Stops when the Stops when the stimulation stopsstimulation stops
Persists after the Persists after the stimulation stopsstimulation stops
1.2 Illuminated bodies.1.2 Illuminated bodies.
Opaque bodiesOpaque bodies allow no light to pass through them allow no light to pass through them
Translucent bodies:Translucent bodies: some light passes through but the some light passes through but the light is scattered and does not allow the shapes of light is scattered and does not allow the shapes of objects to be distinguished.objects to be distinguished.
Transparent bodiesTransparent bodies: light passes through without being : light passes through without being scattered, allowing the shapes of objects to be scattered, allowing the shapes of objects to be distinguished.distinguished.
2. WHAT IS LIGHT?2. WHAT IS LIGHT?
Light is part of a large family of waves with Light is part of a large family of waves with similar properties: similar properties: electromagnetic waveselectromagnetic waves..
All electromagnetic waves travel at the same All electromagnetic waves travel at the same speed ‘speed ‘cc’ in a vacuum or in air: ’ in a vacuum or in air:
c = 300 000 km/sc = 300 000 km/s
In other media (water, glass, diamond…), In other media (water, glass, diamond…), the speed of light, denoted the speed of light, denoted vvmediummedium , is less , is less than than cc
vvmediummedium < < cc
vvwaterwater = 225 000 km/s= 225 000 km/s vvglassglass = 200 000 km/s= 200 000 km/s vvdiamonddiamond = 120 000 km/s= 120 000 km/s
Rather than giving the value of vRather than giving the value of vmedium medium
, we prefer to give the , we prefer to give the refractive refractive indexindex of the medium, denoted n of the medium, denoted nmedium medium
and defined by:and defined by:cc
vvmediummedium
nnmediummedium = =
Calculate the refractive indices of Calculate the refractive indices of water, glass and diamond.water, glass and diamond.
nnwater water = 1.33= 1.33 nnglass glass = 1.5= 1.5 nndiamond diamond = 2.5= 2.5
3. The hypothesis of geometrical 3. The hypothesis of geometrical opticsoptics
3.1. Experiment3.1. Experiment Experimental setupExperimental setup
Conclusion : in a homogenous Conclusion : in a homogenous transparent medium, transparent medium, light travels in light travels in a straight linea straight line..
homogenoushomogenous : having the same properties : having the same properties throughoutthroughout
3.2. Schematic representation3.2. Schematic representation We represent the path of the light by We represent the path of the light by
a straight line called the a straight line called the light raylight ray. . The arrow indicates the direction of The arrow indicates the direction of travel of the light.travel of the light.
Light from a point source spreads in Light from a point source spreads in all directions.all directions.
4. Applications4. Applications
4.1. 4.1. The pinhole cameraThe pinhole camera Experimental setupExperimental setup
A'A'
B'B'
C'C'
Interpretation : the formation of the Interpretation : the formation of the inverted image is explained by the inverted image is explained by the straight line (rectilinear) propagation straight line (rectilinear) propagation of light.of light.
4.2. 4.2. ShadowsShadows object illuminated by a point source object illuminated by a point source
SSPointPoint
source source Large sphereLarge sphere
SmallSmallspheresphere
screenscreen
object illuminated by an extended sourceobject illuminated by an extended source
screenscreen
SSExtendedExtendedsource source
spheresphere