Light 3

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Science Realted facts on LIGHT for Primary School 5th/6th Class

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  • Learning Objectives Children should learn that we see light sources because light from the source enters our eyes
  • Learning Objectives Children should learn that shadows change in length and position throughout the day to measure the length of the shadow in standard measures to make a table and bar chart to show how the length of the shadows changes during the day
  • Learning Objectives Children should learn that shadows are formed when light travelling from a source is blocked to make and record observations and to present information in drawing and writing
  • Learning Objectives Children should learn that it is the Earth that moves, not the Sun, and the Earth spins on its axis once every 24 hours that it is daytime in the part of the Earth facing the Sun and night-time in the part of the Earth away from the Sun
  • Light 3

    1. 1. Light Seán Finn Department of Education UCC
    2. 2. Light sources . All of these objects can be seen in the dark because they let out their own light-they are luminous
    3. 4. How do we see objects that do not let out their own light i.e. non luminous bodies? <ul><li>We can see them when light from another source reflects from them. </li></ul><ul><li>We will not be able to see these objects in the dark. </li></ul>Killarney by night
    4. 5. Light travels from a source When it is ABSOLUTELY DARK you cannot see anything at all … but you cannot see it There might be something HERE …
    5. 6. Light travels from a source … bounces off it and travels to your EYE … … and NOW you can see it But in the daylight RAYS OF LIGHT from the SUN travel to this object…
    6. 7. Light travels from a source There are actually many RAYS OF LIGHT bouncing off the object but the diagrams become too complicated if you put them all in
    7. 9. Do all substances allow light to pass through them? Light will not pass through substances like aluminium foil. Light will pass easily through substances like glass Some light will pass through certain substances
    8. 10. Opaque materials do not allow light to pass through them.
    9. 11. Transparent materials Light will pass very easily through some materials cling film glass window plastic bottle They are said to be TRANSPARENT
    10. 12. Translucent materials You cannot SEE through a sheet of greaseproof paper like you can see through glass But if you shine a torch behind the greaseproof paper you can see the light but NOT exactly what the torch looks like
    11. 13. De sign and make a model glasshouse using a plastic bottle that will allow light to pass through A cloche Place thermometer in bottle next to light. Note that the temperature of the air in the bottle increases.
    12. 14. Investigation: Light travels in straight lines. A B C
    13. 15. How light travels … you can see the view out of the other end If you look through a long cardboard tube…
    14. 16. How light travels … you cannot see anything out of the other end If you bend the cardboard tube and then look through it…
    15. 17. How light travels This is because light travels in STRAIGHT LINES The light CANNOT go any further In this tube there is a straight line from one end to the other In this tube there is only a straight line UP TO HERE
    16. 18. How shadows are formed There many of rays of light travelling in STRAIGHT LINES from the torch Some travel PAST the ornament…. … but others “ BUMP INTO ” the ornament and cannot travel any further
    17. 19. Formation of shadows torch the OBJECT is blocking the light here Light from the torch travelling in a straight line CANNOT get behind the OBJECT OBJECT SHADOW on wall
    18. 20. Size of shadows If light was able to travel in CURVES then we would not get SHADOWS BUT LIGHT ONLY TRAVELS IN STRAIGHT LINES
    19. 21. Size of shadows As the toy is moved towards the wall the shadow gets smaller shadow getting smaller
    20. 22. Size of shadows shadow getting smaller
    21. 23. Size of shadows shadow getting smaller
    22. 24. Size of shadows shadow getting smaller
    23. 25. Size of shadows LARGE SHADOW when the toy is close to the light SMALLER SHADOW when the toy is further from the light TINY SHADOW when the toy is a long way from the light
    24. 26. Formation of shadows
    25. 27. Shadow puppets By using a mixture of opaque , translucent and transparent materials you can create shapes to produce shadow puppets Here a simple cardboard shape ( opaque ) has holes made in it ( transparent ) to provide eyes and a mouth
    26. 28. Shadow puppets This is a picture of a very complicated shadow puppet It is made from opaque wire and transparent materials that are also coloured giving the shadow produced a very colourful appearance
    27. 29. Shadows from the sun Here you can see shadows formed outside by the SUN Notice that the shadows are different sizes at different times of the day SHORT , VERY DARK shadow LONG , LIGHTER shadow
    28. 30. Shadows from the sun To see how shadows change during the day stand in a FIXED position and then get someone to draw round your shadow using chalk or water-based paint A few hours later stand in EXACTLY the same place and again get some one to draw around your shadow
    29. 31. Shadows from the sun This will show you how much shadows change over a few hours To see how shadows change during the day stand in a FIXED position and then get someone to draw round your shadow using chalk or water-based paint A few hours later stand in EXACTLY the same place and again get some one to draw around your shadow
    30. 32. Measuring shadows
    31. 33. Measuring the length of shadows On a SUNNY day set up a stick on a clear piece of ground Using a ruler CAREFULLY measure the length of the shadow Notice what time it is and then record your result in a table like this
    32. 34. Table of results EVERY HOUR go back to the stick and again measure the length of the shadow 4.00 pm 3.00 pm 2.00 pm 1.00 pm 12.00 noon 11.00 am 10.00 am 47 cm 9.00 am Length of shadow Time
    33. 35. Size of shadows 10.00 am 12.00 noon 2.00 pm 4.00 pm
    34. 36. Table of results These results can then be put into a BAR CHART to help you see a PATTERN in your results 49 cm 4.00 pm 45 cm 3.00 pm 42 cm 2.00 pm 35 cm 1.00 pm 22 cm 12.00 noon 37 cm 11.00 am 43 cm 10.00 am 47 cm 9.00 am Length of shadow Time
    35. 37. Shadows during the day The bar chart shows that the shadow is shortest at 12 noon
    36. 38. Light and dark This is a ray of light shining from a torch Put a comb in front of the torch The comb lets light through the gaps, but stops it passing through the prongs The light is broken up into dark and light stripes
    37. 39. Day and night
    38. 40. The Earth moves, the Sun stays still This is the Sun This is the EARTH looking down on the Arctic These are the rays from the SUN lighting up the EARTH This is the half of the Earth that light from the Sun reaches - DAY This is the half that light from the Sun does NOT reach - NIGHT
    39. 41. The sun gives us heat and light without which we could not live
    40. 42. Light is a form of energy
    41. 43. Experiment: To make a solar panel Perspex sheet Water Thermometer
    42. 44. Light is made up of seven colors. -The spectrum
    43. 45. Making a spectrum
    44. 46. The rainbow.
    45. 47. Making a spectrum
    46. 48. Making a spectrum
    47. 49. Mixing of light
    48. 50. Not all objects reflect light. <ul><li>Black objects absorb all light and do not reflect any. </li></ul><ul><li>White objects reflect all light </li></ul><ul><li>Red objects absorb blue and green light and reflect red light. </li></ul>
    49. 51. Reflection <ul><li>We see most objects because they reflect light. </li></ul><ul><li>Most objects reflect light is a diffuse way. </li></ul><ul><li>In some objects that are smooth and opaque regular reflection occurs. </li></ul>
    50. 52. Activity: To investigate reflection <ul><li>Place mirror on white paper. </li></ul><ul><li>Shine a ray into the mirror at an angle. </li></ul><ul><li>Note the position of the reflected ray. </li></ul><ul><li>Change the angle at that the ray makes by moving the light box. </li></ul>Ray box Mirror
    51. 53. The periscope Two mirrors parallel to each other at 45 0
    52. 54. Making a periscope
    53. 55. Curved mirrors
    54. 56. Concave mirror Concave mirors can produce images that are right way up or upside down also larger or smaller. If you place your face close to the mirror your image will by magnified and right way up. Use: Shaving and make-up mirrors
    55. 58. Convex mirrors <ul><li>Always produce an image that is right way up and diminished. </li></ul><ul><li>They are used seeing around corners and in shops for security. </li></ul>
    56. 59. Refraction
    57. 60. To investigate refraction <ul><li>Shine a ray of light through a glass block at an angle. </li></ul><ul><li>Look at the ray of light in the glass from above. </li></ul><ul><li>Increase the angle between the glass and the ray box. </li></ul><ul><li>What do you notice? </li></ul>
    58. 61. Why does refraction occur?
    59. 62. Refraction
    60. 63. To investigate refration in a liquid
    61. 65. Lenses
    62. 66. E xplore how objects may be magnified using simple lens or magnifier
    63. 67. Lenses opperate due to refraction
    64. 68. Use of lenses <ul><li>Camera </li></ul><ul><li>Telescope </li></ul><ul><li>Binoculars </li></ul><ul><li>Glasses </li></ul><ul><li>Microscopes </li></ul>
    65. 69. The telescope <ul><li>Two convex lenses, the objective and the eyepiece. </li></ul><ul><li>Eyepiece has a short focal length </li></ul><ul><li>Objective has a long focal length </li></ul><ul><li>Object to be observed at least 10 m away. </li></ul><ul><li>Telescope has to be focused by varying distance between lenses (sum of focal lengths) </li></ul><ul><li>Magnification is the ratio of focal lengths </li></ul>
    66. 70. B e aware of the dangers of excessive sunlight dangers of looking directly at the sun effect of the sun ’ s rays on skin <ul><li>Sunlight contains ultra-violet (UV)light. </li></ul><ul><li>If sunlight enters the eye it will kill the cells of the retina. These will not grow back. </li></ul><ul><li>. UV light on the skin causes sunburn and aging of the skin and may caues skin cancer. </li></ul><ul><li>Suncream absorbs UV light </li></ul>
    67. 71. The telescope
    68. 72. D esign and make model telescopes Tubing Plastic wrap
    69. 73. A ppreciate the importance of sight The iris controlls the amount of light entering the eye Bright Dark
    70. 74. Structure of the eye The lense of the eye focuses light onto the retina which is carried to the brain via the optic nerve
    71. 75. U nderstand the role of sunlight in photosynthesis <ul><li>Plants make their own food using sunlight in a process called photosnthesis. </li></ul><ul><li>Without light plants cannot grow. </li></ul><ul><li>We eat plants for food or we eat animals/ animal products that have eaten plants. </li></ul>
    72. 76. Why the Moon seems to change The MOON looks different depending on where it is in relation to the SUN From the Earth you cannot see any light hitting the Moon in this position New Moon This is what the Moon looks like from Earth
    73. 77. Why the Moon seems to change Waxing crescent This is what the Moon looks like from Earth
    74. 78. Why the Moon seems to change Last quarter This is what the Moon looks like from Earth
    75. 79. Why the Moon seems to change Waxing gibbous This is what the Moon looks like from Earth
    76. 80. Why the Moon seems to change Full Moon This is what the Moon looks like from Earth
    77. 81. Why the Moon seems to change Waning gibbous This is what the Moon looks like from Earth
    78. 82. Why the Moon seems to change Waning crescent This is what the Moon looks like from Earth
    79. 83. To demonstrate why the shape of the Moon changes
    80. 84. Solar Eclipse
    81. 85. Lunar Eclipse
    82. 86. It is VERY DANGEROUS to look DIRECTLY at the Sun or at a REFLECTION of the Sun – it could make you BLIND
    83. 87. Infants and Junior Classes (Teacher guidelines) <ul><li>Identify different light sources </li></ul><ul><li>Explore the effect of light on materials </li></ul><ul><li>Identify materials that are transparent or opaque. </li></ul><ul><li>Experiment with shadows and reflections </li></ul>
    84. 88. Middle and senior classes (Teacher guidelines) <ul><li>Distinguish between natural and artificial sources of light. </li></ul><ul><li>Explore that white light is made up of many different colours. </li></ul><ul><li>Investigate how light rays change direction as they pass through water and learn that this process is called refraction. </li></ul><ul><li>Understand that mirrors and other shiney surfaces can change the direction of light. </li></ul><ul><li>Explore how lenses are used to make things look bigger and smaller. </li></ul>
    85. 89. Science Curriculum. Infant and Junior Classes
    86. 90. Science Curriculum. First and second classes
    87. 91. Science Curriculum. Third and fourth classes
    88. 92. Science Curriculum. Fifth and sixth classes

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