# 5.1 Slide Reflection of Light

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CHAPTER 5 : LIGHTReflection Of Light

Reflection

Light

Refraction

Lenz LawMirrors Plane Convex mirror Concave mirror

Lenses Convex lens Concave lens

Total internal reflection

Reflection Of Light 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 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.

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.

Reflection Of Light When rays of light strike any surface the rays are reflected , unless the surface is black, when they are absorbed.

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.

Example reflection of lightRegular reflection mirror Difuse reflection Most objects

Example reflection of light

Incident ray

Reflected ray

i

r

Laws of reflection of light: 1. Incident angle = reflected angle i=r 2. The incident ray, the normal and the reflected ray all lie in the same plane

Reflection Of LightAO ON OB i r : Incident ray : Normal Line : Reflected ray : Angle of incidence : Angle of reflection

Reflection Of LightCommon terminology of reflection of light on a plane mirror Normal Line, N : A line at right angles to the mirrors surface. Incident ray, i : A ray of light that is directed onto the mirrors surface. Reflected ray ,r : A ray that is reflected by the mirrors surface.

Reflection Of LightNi rPlane mirror

Angle 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

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

Mirror1. Plane Mirror 2. Curved mirror Concave mirror ( Cermin Cekung ) Convex mirror (Cermin Cembung)

Characteristics of the image Same size as the object Virtual Laterally inverted

Image formed by a plane mirror:

object

A

B

C

Image

i1 r1

Eye

Characteristics of image formed by plane mirror:

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

Differences between real and virtual image:Virtual image Cannot be appear on a screen Formed by the Form at a meeting of real position where rays. rays appear to be originating.Example LCD Projector Example Image from mirror

Real image Can be appear on a screen

45o 45o 45o

100oo 35o 55

55o

Curved Mirror Concave mirror ( Cermin Cekung ) Convex mirror (Cermin Cembung)

Common terminology of reflection of light on a curved mirrorConcave mirror Convex mirror

C

P

C

P

r

r

F

C

Convex Mirror

F C

Concave Mirror

Concave mirror

Convex mirror

C

P

C

P

r

r

C = Centre of curvature r = Radius of curvature P = Pole PC = Principal axis

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.

Concave mirrorPrincipal axis ,PFC : A line which passes through the centre of curvature ,C and the pole of a curved mirror, P

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

Concave mirror Focal length , f : The distance between the principal focus ,F and the pole of the curved mirror, P.

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.

Convex mirrorPrincipal axis ,PFC : A line which passes through the centre of curvature ,C and the pole of a curved mirror, P

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.

Convex mirrorFocal length , f : The distance between the principal focus ,F and the pole of the curved mirror, P.

Relationship between f and r

r = 2f = PC PF = FC

f1 f1 < f2

f2

Relationship curvature of mirror and fThe more curved the mirror , the shorter its focal length, f.

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.

C

F

Image formed by a Concave MirrorF = Focal point C = Centre Of mirror Case 1: u < fConcave mirror object F C F image

Characteristics Of Images : Upright, Virtual , enlarged

Case 2:

u=f

Characteristics Of Images :

C

F

Case 2:Concave mirror object

u=f

F C F

Characteristics Of Images : Enlarged, Virtual , Upright

Case 3: f < u < 2f

Characteristics Of Images :

C

F

Case 3: f < u < 2fConcave mirror object

C

F

F

image

Characteristics Of Images : Enlarged , Inverted , Real

Case 4: u = 2f or u = r

C

F

Case 4: u = 2f or u = rConcave mirror object F C F

image

Characteristics Of Images : Same Size , Inverted , Real

Case 5: u > 2f

Case 5: u > 2f

Characteristics Of Images : Diminished In Size , Inverted ,Real

C

F

Case 6 u = g ( Object ,O very far from the lens)

Case 6 u = g ( Object ,O very far from the lens)

Characteristics Of Images : Real , Inverted , Diminished In Size

Conclusion Concave MirrorThe distance object, u Characteristics of image u < f u =f f 2f u=g Conclusion

VUM

VUM

C

FP

C

FQ

RIM

RIS

C

F

C

FS

R

RID

Figure P Q

Characteristic of image Virtual, Upright, Magnified Virtual, Upright, Magnified Real, Inverted, Magnified Real, Inverted, Same size Real, Inverted, Diminished

C

FT

R S T

Conclusion Concave MirrorThe distance object, u Characteristics of image u < f u =f f 2f u=g Conclusion Upright, Virtual , magnified Magnified, Virtual , Upright Magnified , Inverted , Real Same Size , Inverted , Real Diminished In Size, Inverted , Real Real , Inverted , Diminished In Size

C

F

Image formed by a Convex Mirror1) u < f ( Object between F and P )

Characteristics of image :

Image formed by a Convex Mirror1) u < f ( Object between F and P )

Characteristics of image : Virtual, Upright , Diminished In Size

2) f < u < 2f or f < u < C ( Object O is between F and C.)

Characteristics of image :

2) f < u < 2f or f < u < C ( Object O is between F and C.)

Characteristics of image : Diminished In Size, Upright, Virtual

3) u > 2f (Object, O is beyond C)

Characteristics of image :

3) u > 2f (Object, O is beyond C)

Characteristics of image : Diminished In Size, Upright, Virtual

Conclusion Convex MirrorThe Characteristics of image distance object, u u < f f < u < 2f u > 2f Conclusion

F

C

F

C

X Figure X F C Y Z Z

Y Characteristic of image Upright, diminished, virtual Upright, diminished, virtual Upright, diminished, virtual

Conclusion:

Conclusion Convex MirrorThe distance object, u u < f f < u < 2f u > 2f Conclusion Characteristics of image

Diminished In Size, Upright, Virtual Diminished In Size, Upright, Virtual Diminished In Size, Upright, Virtual Diminished In Size, Upright, Virtual

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

Application reflection of light2) A mirror periscope can be built by mounting two plane mirror

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