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8 k light (whs)


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8 k light (whs)

  1. 1. 30/03/2014 KS3 Light
  2. 2. 30/03/2014 Properties of Light Light travels in straight lines: Laser
  3. 3. 30/03/2014 Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.
  4. 4. 30/03/2014 Light travels much faster than sound. For example: 1) Thunder and lightning start at the same time, but we will see the lightning first. 2) When a starting pistol is fired we see the smoke first and then hear the bang.
  5. 5. 30/03/2014 We see things because they reflect light into our eyes: Homework
  6. 6. 30/03/2014 Luminous and non-luminous objects A luminous object is one that produces light. A non-luminous object is one that reflects light. Luminous objects Reflectors
  7. 7. 30/03/2014 Shadows Shadows are places where light is “blocked”: Rays of light
  8. 8. 30/03/2014 Properties of Light summary 1) Light travels in straight lines 2) Light travels much faster than sound 3) We see things because they reflect light into our eyes 4) Shadows are formed when light is blocked by an object
  9. 9. 30/03/2014 Reflection Reflection from a mirror: Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror
  10. 10. 30/03/2014 The Law of Reflection Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at the SAME angle it hits it. The same !!!
  11. 11. 30/03/2014 Clear vs. Diffuse Reflection Smooth, shiny surfaces have a clear reflection: Rough, dull surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions
  12. 12. 30/03/2014 Using mirrors Two examples: 1) A periscope 2) A car headlight
  13. 13. 30/03/2014 Colour White light is a mixture of the seven colours of the rainbow. White light can be split by a PRISM Rainbows form when sunlight is split by raindrops.
  14. 14. 30/03/2014 The colours of the rainbow: Red Orange Yellow Green Blue Indigo Violet
  15. 15. 30/03/2014 Adding colours White light can be split to make separate colours. These colours can be added together again. The primary colours are red, blue and green Adding blue and red makes magenta Adding blue and green makes cyan Adding all three makes white again Adding red and green makes yellow
  16. 16. 30/03/2014 Red GreenBlue Cyan YellowMagenta White
  17. 17. 30/03/2014 Seeing colour The colour an object appears depends on the colours of light it reflects. For example, a red book only reflects red light: White light Only red light is reflected
  18. 18. 30/03/2014 A white hat would reflect all seven colours: A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue): Purple light White light
  19. 19. 30/03/2014 Using coloured light If we look at a coloured object in coloured light we see something different. For example, consider a football kit: White light Shorts look blue Shirt looks red
  20. 20. 30/03/2014 In different colours of light this kit would look different: Red light Shirt looks red Shorts look black Blue light Shirt looks black Shorts look blue
  21. 21. 30/03/2014 Some further examples: Object Colour of light Colour object seems to be Red socks Red Red Blue Black Green Black Blue teddy Red Black Blue Green Green camel Red Blue Green Magenta book Red Blue Green
  22. 22. 30/03/2014 Using filters Filters can be used to “block” out different colours of light: Red Filter Magenta Filter
  23. 23. 30/03/2014 Investigating filters Colour of filter Colours that could be “seen” Red Green Blue Cyan Magenta Yellow
  24. 24. 30/03/2014 Red Magenta White Yellow Blue Green Cyan
  25. 25. 30/03/2014 Refraction through a glass block: Wave slows down and bends towards the normal on entering a more dense medium Wave speeds up and bends away from the normal on entering a less dense medium Wave slows down but is not bent, due to entering along the normal
  26. 26. 30/03/2014
  27. 27. 30/03/2014 Refraction Refraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks like this: In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______. Words – speed up, water, air, bent, medium
  28. 28. 30/03/2014 REFRACTION Refraction is when rays SPEED UP or SLOW DOWN when travelling through a different MEDIUM. E.g. a ruler placed in water: The light rays are slowed down by the water and are BENT. This makes the ruler look bent. The two media in this example are WATER and AIR.