1. LIGHT AND SOUND  Geology Tests  Title page: Homework  LIGHT! Later… Sound

2. Light: It travels in straight lines 16 th September 2010

3. 24/06/2016 Properties of Light  Light travels in straight lines: Laser

4. 24/06/2016  Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.

5. 24/06/2016  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.

6.  We see things because they reflect light into our eyes: 24/06/2016 Homework

7. 24/06/2016  Luminous and non-luminous objects A luminous object is one that produces light. A non-luminous object is one that reflects light. Luminous objectsReflectors

8. 24/06/2016  Shadows Shadows are places where light is “blocked”: Rays of light

9. 24/06/2016 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

10. Colour  White light is not a single colour; it is made up of a mixture of the seven colours of the rainbow. 24/06/2016 We can demonstrate this by splitting white light with a prism: This is how rainbows are formed: sunlight is “split up” by raindrops.

11. The colours of the rainbow:  Red  Orange  Yellow  Green  Blue  Indigo  Violet 24/06/2016

12. Red Green Blue Cyan Yellow Magenta White

13. Adding colours  White light can be split up to make separate colours. These colours can be added together again.  The primary colours of light are red, blue and green: 24/06/2016 Adding blue and red makes magenta (purple) Adding blue and green makes cyan (light blue) Adding all three makes white again Adding red and green makes yellow

14. Using filters  Filters can be used to “block” out different colours of light: 24/06/2016 Red Filter Magenta Filter

15. Investigating filters 24/06/2016 Colour of filterColours that could be “seen” Red Green Blue Cyan Magenta Yellow

16. Adding colours  White light can be split up to make separate colours. These colours can be added together again.  The primary colours of light are red, blue and green: 24/06/2016 Adding blue and red makes magenta (purple) Adding blue and green makes cyan (light blue) Adding all three makes white again Adding red and green makes yellow

17. Seeing colour  The colour an object appears depends on the colours of light it reflects. 24/06/2016 For example, a red book only reflects red light: White light Only red light is reflected

18. 24/06/2016 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. Using coloured light  If we look at a coloured object in coloured light we see something different. For example, consider a football kit: 24/06/2016 White light Shorts look blue Shirt looks red

20.  In different colours of light this kit would look different: 24/06/2016 Red light Shirt looks red Shorts look black Blue light Shirt looks black Shorts look blue

21. Some further examples: 24/06/2016 ObjectColour of light Colour object seems to be Red socks Red BlueBlack GreenBlack Blue teddy RedBlack Blue Green Green camel Red Blue Green Magenta book Red Blue Green

22. 24/06/2016 Red Magenta White Yellow BlueGreen Cyan

23. Five QUICK Review Questions  1. The fastest time recorded to solve a rubrics cube is 6 seconds, which is held by an Australian man. ~ How many times did a single beam of light travel around the earth during this time?  2. Explain the difference between reflection and refraction

24. Five QUICK Review Questions contd…  3. Which of the following is NOT a luminous object? a) Bon fire b) Diamond c) Glow worm d) The sun e) Torch

25. Five QUICK Review Questions contd…  4. What colour or colours are being reflected off each of the following objects when they are placed under white light? a) Magenta pencil b) Green apple c) Yellow mini d) Black cat

26. Five QUICK Review Questions contd…  5. What colour would each of the following appear a) a red rose in white light b) a blue gumboot in red light c) a green cow in green light yellow d) yellow ducks in green light e) blue blueberries in magenta light yellow f) a black swan in yellow light

27. Answers  1. Light travels at 300000km every second. This is 8 times around the world. In 6 seconds it could travel 48 times around the world (6x8=48)  2. Reflection is the BOUNCING off of light but Refraction is the BENDING of light as it travels through different transparent (see through) mediums  3. Diamond is the NON luminous object. It is a very good reflector though: very sparkly  4. What colour or colours are being reflected off each of the following objects when they are placed under white light? a) Magenta pencil: BLUE AND RED b) Green apple: GREEN c) Yellow mini: RED AND GREEN d) Black cat: NO COLOURS- all absorbed

28.  5. What colour would each of the following appear a) a red rose in white light: RED b) a blue gumboot in red light: BLACK c) a green cow in green light: GREEN yellow d) yellow ducks in green light: GREEN e) blue blueberries in magenta light: BLUE yellow f) a black swan in yellow light: BLACK

29. WORKSHEET ON SHADOWS  Complete the worksheet on shadows then stick it into you workbooks

30. 24/06/2016 Reflection  Reflection from a mirror: Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror

31. 24/06/2016  The Law of Reflection Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at ____ _____ angle it hits it. The same !!!

32. 24/06/2016 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

33. WORKSHEET  1. PUT YOUR NAME AT THE TOP  2. Complete the questions using your notes UP TO THE YELLOW HIGHLIGHTED QUESTION on page two

34. HOMEWORK!  Hand to the front your light homework AND your eye diagram.

35. Recap Questions:  1. What is the function of the CORNEA in the eye???  2. What colours make up white light?  3. What is the difference between a clear and a diffuse reflection?  4. Give one object you would expect to get a clear reflection from  5. Give one object you would expect to get a diffuse reflection from  6. What colour would a CYAN octopus look in green light?

36. Refraction  When light travels from one transparent (see through) material to another it changes direction.  We call this refraction.  Refraction takes place because the speed of light is different in different materials.  The ray of light bends more towards the normal in materials where it travels more slowly= more dense materials.  Speed of light in;  Air: 300 000 km/s  Water: 225 000 km/s  Diamond:124 000 km/s  Perspex: 201 000 km/s  Glass:197 000 km/s

37. 24/06/2016 Refraction (is when light is BENT) ~Through a glass block: Wave slows down and bends towards the normal due to entering a more dense medium Wave speeds up and bends away from the normal due to entering a less dense medium Wave slows down but is not bent, due to entering along the normal

38. 24/06/2016

39. 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

40. Convex: a convex mirror or lens is shaped like this

41. Concave: a concave mirror or lens is shaped like this

42. REFLECTION off a CONVEX surface Light Source

43. REFLECTION off a CONCAVE surface Light Source

44. REFRACTION Convex lens Concave lens Focus point

45. Where is REFRACTION used?  Our eyes

46. Our eyes… Camera…