5.1 slide reflection of light
TRANSCRIPT
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CHAPTER 5 : LIGHT
Reflection Of Light
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Light
Mirrors Lenses
Plane
Convex mirror
Concave mirror
Convex lens
Reflection Refraction
Concave lens
Lenz Law
Total internalreflection
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• Light is a form energy that enables us to see.
• Light is emitted or given by hot objects, like a candle flame, or the glowing filament of light bulb, or the sun.
• An object which produces its own light is said to be luminous.
• Most of the objects we can see do not produce their own light – they are non-luminous. What we can see is the light is reflected off them. Example like cloths, rock, face and etc.
Reflection Of Light
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Reflection Of Light• Light seems to travel in straight lines.
A picture of light as rays traveling in straight lines from a luminous source or bouncing off objects, or being absorbed or transmitted by them, is very useful one.
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Reflection Of Light• We can think of light ray as a very
thin beam of light. A real beam contains many rays. But by drawing just a few of them we can get a clear idea of what happening to the whole beam.
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Reflection Of Light• When rays of light strike any surface the
rays are reflected , unless the surface is black, when they are absorbed.
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Reflection Of Light• The reflection depend on how smooth the
surfaces are. Good mirrors reflect well over 90% of the light that reaches them, with only a small amount being absorbed.
• The surface of most objects are very irregular. Light hitting this sort of surface is scattered in all directions. This is called diffuse reflection.
• On the other hand, the surface of a polished sheet of glass or metal can be made extremely smooth. The reflection from this is the regular.
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mirror
Most objects
Regular reflection
Difuse reflection
Example reflection of light
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Example reflection of light
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Incident ray Reflected ray
i r
i = r
Laws of reflection of light:
1. Incident angle = reflected angle
2. The incident ray, the normal and the reflected ray all lie in the same plane
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Reflection Of Light
AO : Incident ray
ON : Normal Line
OB : Reflected ray
i : Angle of incidence
r : Angle of reflection
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Reflection Of LightCommon terminology of reflection of light on a plane mirrorNormal Line, N :A line at right angles to the mirror’s surface.
Incident ray, i :A ray of light that is directed onto the mirror’s surface.
Reflected ray ,r :A ray that is reflected by the mirror’s surface.
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Reflection Of LightAngle of incidence, i :
The angle between the
incident ray and the
Normal
Angle of reflection, r :
The angle between the
reflection ray and the
normal line
i rPlane mirror
N
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Laws of Reflection
The Law Of Reflection State That:
• The incident ray, the reflected ray and the normal to the point of incidence, all lie in the same plane.
• The angle of incidence, i = The angle of reflection, r
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Mirror
1. Plane Mirror
2. Curved mirror
– Concave mirror ( Cermin Cekung )
– Convex mirror (Cermin Cembung)
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Characteristics of the image
Same size as the object
Virtual
Laterally inverted
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Image formed by a plane mirror:
object
i1r1
A B C
Eye
Image
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Characteristics of image formed by plane mirror:
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Characteristics of image formed by plane mirror:
i ) virtual
ii) laterally inverted
iii) same size as object
iv) object distance from mirror
= image distance from mirror
v) Upright
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Differences between real and virtual image:
Real image Virtual image
Can be appear on a screen
Cannot be appear on a
screen
Formed by the meeting of real
rays.
Form at a position where rays appear to be originating.
Example LCD Projector
Example Image from mirror
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45o
100o
45o
45o
35o 55o
55o
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Curved Mirror
• Concave mirror ( Cermin Cekung )
• Convex mirror (Cermin Cembung)
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Common terminology of reflection of light on a curved mirror
PC
r
Concave mirror
C
r
P
Convex mirror
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CF
Convex Mirror
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C
F
Concave Mirror
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C = Centre of curvature
r = Radius of curvature
P = Pole
PC = Principal axis
PC
r
Concave mirror
C
r
P
Convex mirror
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Concave mirrorPole of mirror , P :
The centre point on
the curved mirror
Centre of curvature , C
:The geometric centre
of a hollow sphere of
which the concave or
convex mirror is a part.
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Concave mirror
Principal axis ,PFC
: A line which passes
through the centre of
curvature ,C and the
pole of a curved
mirror, P
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Concave mirrorPrincipal focus , F
A point where all rays
traveling parallel to the
principal axis converge or
diverge after reflection
by the mirror.
Radius of curvature, r :
Distance between the
pole, P and the
centre of curvature, C
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Concave mirror
• Focal length , f
: The distance
between the principal
focus ,F and the pole of
the curved mirror, P.
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Convex mirrorPole of mirror , P
: The centre point on
the curved mirror
Centre of curvature , C
: The geometric centre
of a hollow sphere of
which the concave or
convex mirror is a part.
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Convex mirror
Principal axis ,PFC
: A line which passes
through the centre of
curvature ,C and the
pole of a curved
mirror, P
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Convex mirrorPrincipal focus , F
: A point through
which all rays traveling
parallel to the principal axis
converge to or appear to
diverge from after reflection
by the mirror.
Radius of curvature, r
: Distance between
the pole, P and the
centre of curvature, C.
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Convex mirror
Focal length , f
: The distance
between the principal
focus ,F and the pole of
the curved mirror, P.
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Relationship between f and r
r = 2f = PC
PF = FC
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f1 f2
f1 < f2
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Relationship curvature of mirror and f
The more curved the
mirror , the shorter its
focal length, f.
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Image formed by curved mirror (ray diagram method)
Principle of drawing ray diagrams:
1. The position and characteristics of images formed by a concave or convex mirror can be determined by drawing ray diagrams.
2. Images formed by concave or convex mirror can be determine by drawing two of the following rays. A curved mirror is represented by a straight line.
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C F
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Image formed by a Concave Mirror
F = Focal point C = Centre Of mirror
Case 1: u < f
C FF
object
Concave mirror
image
Characteristics Of Images : Upright, Virtual , enlarged
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Case 2: u = f
Characteristics Of Images :
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C F
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Case 2: u = f
C FF
object
Concave mirror
Characteristics Of Images : Enlarged, Virtual , Upright
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Case 3: f < u < 2f
Characteristics Of Images :
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C F
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Case 3: f < u < 2f
C FF
object
Concave mirror
image
Characteristics Of Images : Enlarged , Inverted , Real
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Case 4: u = 2f or u = r
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C F
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Case 4: u = 2f or u = r
C FF
object
Concave mirror
image
Characteristics Of Images : Same Size , Inverted , Real
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Case 5: u > 2f
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Case 5: u > 2f
Characteristics Of Images : Diminished In Size , Inverted ,Real
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C F
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Case 6 u = ( Object ,O very far from the lens)
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Case 6 u = ( Object ,O very far from the lens)
Characteristics Of Images : Real , Inverted , Diminished In Size
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Conclusion Concave Mirror
The distance object, u Characteristics of image
u < f
u = f
f <u < 2f
u = 2f
u > 2f
u = Conclusion
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C F C F
C F C F
C F
Figure Characteristic of image
P
Q
R
S
T
Virtual, Upright, Magnified
Virtual, Upright, Magnified
Real, Inverted, Magnified
P
T
SR
Q
Real, Inverted, Same size
Real, Inverted, Diminished
VUM VUM
RIM RIS
RID
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Conclusion Concave Mirror The distance object, u Characteristics of image
u < f Upright, Virtual , magnified
u = f Magnified, Virtual , Upright
f <u < 2f Magnified , Inverted , Real
u = 2f Same Size , Inverted , Real
u > 2f Diminished In Size, Inverted , Real
u = Real , Inverted , Diminished In Size
Conclusion
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C F
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Image formed by a Convex Mirror
1) u < f ( Object between F and P )
Characteristics of image :
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Image formed by a Convex Mirror
1) u < f ( Object between F and P )
Characteristics of image : Virtual, Upright , Diminished In Size
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2) f < u < 2f or f < u < C ( Object O is between F and C.)
Characteristics of image :
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2) f < u < 2f or f < u < C ( Object O is between F and C.)
Characteristics of image : Diminished In Size, Upright, Virtual
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3) u > 2f (Object, O is beyond C)
Characteristics of image :
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3) u > 2f (Object, O is beyond C)
Characteristics of image : Diminished In Size, Upright, Virtual
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Conclusion Convex Mirror
The distance object, u
Characteristics of image
u < f
f < u < 2f
u > 2f
Conclusion
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F C
F C F C
Figure Characteristic of image
X
Y
Z
X
Z
Y
Conclusion:
Upright, diminished, virtual
Upright, diminished, virtual
Upright, diminished, virtual
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Conclusion Convex Mirror
The distance object, u
Characteristics of image
u < f Diminished In Size, Upright, Virtual
f < u < 2f Diminished In Size, Upright, Virtual
u > 2f Diminished In Size, Upright, Virtual
Conclusion Diminished In Size, Upright, Virtual
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Application reflection of light use in plane mirror
1) A rear view mirror and a side mirror of a car in order to enable the driver see objects at the back and side of the car.
Side mirror Of Car
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Application reflection of light
2) A mirror periscope can be built by mounting two plane mirrors in a cardboard tube.
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Application reflection of light
3)Plane mirror acts as an anti-parallax error mirror in electrical instruments such as the voltmeter and the ammeter.
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Application Of Concave mirror
(1) A shaving mirror or a make-up mirror
used a wide-aperture concave mirror with a large radius of curvature.
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(2) A torchlight or a headlight of motor vehicles used concave
parabolic mirror to produce a beam of parallel light rays.
ONOFF
Car head lampCurved mirror
lamp
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LOW BEAM
HIGH BEAM
Motor vehicles used concave parabolic mirror for high beam and low beam
Sometimes motor vehicles used difference of filament to produce high and low beam
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3) Convex mirror are mounted at a sharp corner of a road so that the drivers are able to see oncoming cars on the blind side of the corner.
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Convex mirror4)Convex mirror hung on the corner of
ceilings in supermarkets serve to provide a wide field of view activities happening in the shopping area.