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- 2. 30/03/2014 Properties of Light Lighttravels in straight lines: Laser
- 3. 30/03/2014 Light travels VERYFAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.
- 4. 30/03/2014 Light travels muchfaster 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. 30/03/2014 We see thingsbecause they reflect light into our eyes: Homework
- 6. 30/03/2014 Luminous and non-luminousobjects A luminous object is one that produces light. A non-luminous object is one that reflects light. Luminous objects Reflectors
- 7. 30/03/2014 Shadows Shadows are placeswhere light is “blocked”: Rays of light
- 8. 30/03/2014 Properties of Lightsummary 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. 30/03/2014 Reflection Reflection from amirror: Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror
- 10. 30/03/2014 The Law ofReflection 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. 30/03/2014 Clear vs. DiffuseReflection 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. 30/03/2014 Using mirrors Two examples: 1)A periscope 2) A car headlight
- 13. 30/03/2014 Colour White light isa 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. 30/03/2014 The colours ofthe rainbow: Red Orange Yellow Green Blue Indigo Violet
- 15. 30/03/2014 Adding colours White lightcan 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
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- 17. 30/03/2014 Seeing colour The colouran 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. 30/03/2014 A white hatwould 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. 30/03/2014 Using coloured light Ifwe 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. 30/03/2014 In different coloursof light this kit would look different: Red light Shirt looks red Shorts look black Blue light Shirt looks black Shorts look blue
- 21. 30/03/2014 Some further examples: ObjectColour 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. 30/03/2014 Using filters Filters canbe used to “block” out different colours of light: Red Filter Magenta Filter
- 23. 30/03/2014 Investigating filters Colour offilter Colours that could be “seen” Red Green Blue Cyan Magenta Yellow
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- 25. 30/03/2014 Refraction through aglass 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
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- 27. 30/03/2014 Refraction Refraction is whenwaves ____ __ 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. 30/03/2014 REFRACTION Refraction is whenrays 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.