# Reflection ( 反射 ) incident rayreflected ray plane mirror angle of incidence angle of reflection normal Reflection of Light ( 光的反射 )

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• Reflection ()

• incident rayreflected rayplane mirrorangle of incidenceangle of reflectionnormalReflection of Light ()

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Incident Rays()The light ray moving towards the mirror Reflected Rays()The light ray moving out of the mirrorNormal()The line perpendicular () to the mirrorAngle of incidence()The angle between the incident ray and the normal.Angle of reflection()The angle between the reflected rays and the normal.

• incidentrayreflectedrayLaws of reflection:The angle ofreflection requal toof incidence i.plane mirrorir1.isthe anglenormalvertical planeLaws of reflection () i = r

• Laws of reflection:The incident ray,the reflected rayand the normalall lie in the sameplane.incidentrayreflectedraynormalplane mirrorvertical plane2.

• *When the angle of incidence equals to zero (i = 0) , the angle of reflection is also zero (r = 0).

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• *4040606030304545

• *5.3 Experiment ()

• *Conclusion ()The angle of incidence is ____________ the angle of reflection.

i /030456075r /

• *Conclusion ()The angle of incidence is _equal to_ the angle of reflection.

i /030456075r /030456075

• Will the reflected rays remain parallel () after reflection?

Regular reflection ()

• same isame r The reflected rays are therefore parallel.iiirrrparallel incident raysparallel reflected raysplane mirror Each light ray obeys the laws of reflection.For flat () and smooth () surface,

• plane mirrorRegular reflection () occurs at:

• The following reflecting surfaces can form clear images due to regular reflection.a calm water surfacemetal surface

• For rough () surface,i1i2i3r1r2r3rough surfaceparallel incident raysreflected rays are not parallelEach light ray obeys the laws of reflection.different idifferent rDiffuse reflection ()

• Diffuse reflection occurs at a rough surface (e.g. a piece of paper).e.g. a piece of paper

• Lateral inversion ()Mirror images are laterally inverted.

• The laterally inverted words on an ambulance ()the objectimage formed by the plane mirror

• An image formed by a plane mirror is1. same size as the object,2. laterally inverted. ()3. same distance

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• *Uses of plane mirrors () rear-view mirrors ()

• *Explain why the Chinese characters are printed in the special way as shown.

• *So that the driver of the car in front of the ambulance can see the Chinese characters without lateral inversion.

• Periscope () A periscope consists of two mirrors The mirrors make an angle of 45 with the line joining them.

• Periscopes are used in a double-deckers ()

• *Periscope () used in submarine ().

• *Plane mirrors used in interior design ().

• *Plane mirror used by dentist ().

• *In Figure 5.4, draw ONE light ray from the head of the object to the eye after reflection from the two mirrors.

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• *Homework: Assignment Book 1. Chapter 5 Q.1 Q.8 (p.7-9) 2. Deadline:

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