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# Physics - Light

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This corresponds to the "Light" component of Waves in the GCE 'O' Level - Physics (Pure) syllabus.

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### Physics - Light

1. 1. This presentation was produced by the Science department ofTemasek Secondary School. Redistribution or reproduction ofthis resource is prohibited by copyright regulations. This resourceshould be used for educational purposes.
2. 2. LIGHTReflection of LightRefraction of LightLenses
3. 3. NATURE OF LIGHT• Light is a form of energy.• Light is a form of wave motion.The way in which light radiates from its source is similarto the way in which ripples spread outwards across apond.
4. 4. NATURE OF LIGHT• Light travels at a speed of 3 x 108m/sthrough empty space.• Light can be detected by human eye.This speed is equivalent to travelling 7 times roundthe Earth in less than a second!• Light travels in straight lines.
5. 5. • Light travels in straight lines.
6. 6. • Light travels in straight lines.
7. 7. EXPERIMENT TO DEMONSTRATE RECTILINEAR PROPAGATIONApparatus: 3 card board screens having small holes in their centers.Candle or lamp.
8. 8. LIGHT RAYS• The path along which light energy travelsis called a ray.A light ray• A bundle of light rays is a beam of light.Line represents the path along which light travels.Arrow represents the direction in which light travels.
9. 9. LIGHT BEAMS• 3 different types of light beams :Parallel Beam : Light rays travels from very far awayDivergent Beam : Light rays from a point source (not faraway)Convergent Beam : Light rays meet at a point
10. 10. REFLECTION OF LIGHT• We can see luminous objects: as they give offlight which enters our eyes.Non-luminous objects: as they reflectlight from a source to our eyes.
11. 11. TERMS USED IN THESTUDY OF REFLECTION• A reflecting surfaceAny shiny (smooth) surface.E.g a plane mirrorSymbol of a plane mirrorreflecting surface
12. 12. TERMS USED IN THESTUDY OF REFLECTION• The incident rayThe ray that approaches the mirror.incident ray
13. 13. TERMS USED IN THESTUDY OF REFLECTION• The reflected rayThe ray that bounces off the mirror.reflected rayincident ray
14. 14. TERMS USED IN THESTUDY OF REFLECTION• The point of incidenceThe point where the incident ray meets the mirror.reflected rayincident raypoint of incidence
15. 15. TERMS USED IN THESTUDY OF REFLECTION• The normalThe line that is perpendicular (at 90o) to the mirror.normalreflected rayincident ray
16. 16. TERMS USED IN THESTUDY OF REFLECTION• The angle of incidence, iThe angle between the incident ray and the normal.normalreflected rayincident rayi
17. 17. TERMS USED IN THESTUDY OF REFLECTION• The angle of reflection, rThe angle between the reflected ray and the normal.normalreflected rayincident rayi r
18. 18. TERMS USED IN THESTUDY OF REFLECTION
19. 19. LAWS OF REFLECTION• The angle of incidence is equal to theangle of reflection.i = rnormalreflected rayincident rayi r
20. 20. LAWS OF REFLECTION• The incident ray, the reflected ray andthe normal at the point of incidence alllie on the same plane.We always see all of them on the flat piece ofsurface.
21. 21. LAWS OF REFLECTION
22. 22. IMAGE IN A PLANE MIRROR• The image is virtual.• The image is upright.• The image formed has the same size asthe object.Image cannot be formed on the screen.Light rays do not meet at the image position.It is an imaginary image.
23. 23. IMAGE IN A PLANE MIRROR• The image is as far behind the mirror asthe object is in front of the mirror.Object distance d1 = Image distance d2d1d2
24. 24. IMAGE IN A PLANE MIRROR• The image is laterally inverted (left-to-right inversion)Left side of the object becomes the right side of the image.
25. 25. APPLYING THELAWS OF REFLECTION• To locate image formed in a plane mirror.EYEO
26. 26. RAY DIAGRAMSStep 1 : Locate the image position.EYEIO
27. 27. RAY DIAGRAMSStep 2 : Draw reflected rays(connect Image I to eye)EYEIO
28. 28. RAY DIAGRAMSStep 2 : Draw incident rays.(connect object O to reflected rays)EYEIO
29. 29. • To draw the mirror image of an object.APPLYING THELAWS OF REFLECTION
30. 30. USING REFLECTION• Periscope• Mirror in meter• Optical testing• Other uses