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- 1. Light Seán Finn Department ofEducation UCC
- 2. Light sources. All ofthese objects can be seen in the dark because they let out their own light-they are luminous
- 4. How do wesee objects that do not let out their own light i.e. non luminous bodies? • We can see them when light from another source reflects from them. • We will not be able to see these objects in the dark. Killarney by night
- 5. Light travels froma source When it is ABSOLUTELY DARK you cannot see anything at all There might be something HERE … …but you cannot see it
- 6. Light travels froma source …bounces off it and travels to your EYE EYE… But in the daylight RAYS OF LIGHT RAYS OF LIGHT from the SUN SUN travel to this object… …and NOW NOW you can see it
- 7. Light travels froma source There are actually many RAYS OF RAYS OF LIGHT LIGHT bouncing off the object but the diagrams become too complicated if you put them all in
- 9. Do all substancesallow 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
- 10. Opaque materials donot allow light to pass through them.
- 11. Transparent materials Light willpass very easily through some materials cling film glass window plastic bottle They are said to be TRANSPARENT
- 12. Translucent materials You cannotSEE 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
- 13. D esign andmakea model glasshouseusing a plastic bottlethatwill allow lightto pass through A cloche Place thermometer in bottle next to light. Note that the temperature of the air in the bottle increases.
- 14. Investigation: Light travelsin straight lines. A B C
- 15. How light travels …youcan see the view out of the other end If you look through a long cardboard tube…
- 16. How light travels …youcannot see anything out of the other end If you bend the cardboard tube and then look through it…
- 17. How light travels Thisis because light travels in STRAIGHT LINES 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 The light CANNOT go any further
- 18. How shadows areformed There many of rays of light travelling in STRAIGHT LINES STRAIGHT LINES from the torch Some travel PAST PAST the ornament…. …but others “BUMP BUMP INTO INTO” the ornament and cannot travel any further
- 19. Formation of shadows torch theOBJECT OBJECT is blocking the light here Light from the torch travelling in a straight line CANNOT CANNOT get behind the OBJECT OBJECT OBJECT OBJECT SHADOW SHADOW on wall
- 20. Size of shadows Iflight was able to travel in CURVES CURVES then we would not get SHADOWS SHADOWS BUT LIGHT ONLY TRAVELS IN STRAIGHT LINES
- 21. Size of shadows Asthe toy is moved towards the wall the shadow gets smaller shadow getting smaller
- 22. Size of shadows shadowgetting smaller
- 23. Size of shadows shadowgetting smaller
- 24. Size of shadows shadowgetting smaller
- 25. Size of shadows LARGESHADOW 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
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- 27. By using amixture of opaque, translucent and transparent materials you can create shapes to produce shadow puppets Shadow puppets Here a simple cardboard shape (opaque) has holes made in it (transparent) to provide eyes and a mouth
- 28. This is apicture 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 Shadow puppets
- 29. Shadows from thesun 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
- 30. Shadows from thesun 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
- 31. Shadows from thesun 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
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- 33. Measuring the lengthof 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
- 34. Table of results 4.00pm 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 EVERY HOUR go back to the stick and again measure the length of the shadow
- 35. Size of shadows 10.00am 12.00 noon 2.00 pm 4.00 pm
- 36. Table of results 49cm 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 These results can then be put into a BAR CHART to help you see a PATTERN in your results
- 37. Shadows during theday 0 5 10 15 20 25 30 35 40 45 50 Length of shadow (cms) 9 am 10 am 11 am 12 noon 1 pm 2 pm 3 pm 4 pm Time The bar chart shows that the shadow is shortest at 12 noon
- 38. Light and dark Thelight is broken up into dark and light stripes 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
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- 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
- 41. The sun givesus heat and light without which we could not live
- 42. Light is aform of energy
- 43. Experiment: To makea solar panel Perspex sheet Water Thermometer
- 44. Light is madeup of seven colors. -The spectrum
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- 50. Not all objectsreflect light. • Black objects absorb all light and do not reflect any. • White objects reflect all light • Red objects absorb blue and green light and reflect red light.
- 51. Reflection • We seemost objects because they reflect light. • Most objects reflect light is a diffuse way. • In some objects that are smooth and opaque regular reflection occurs.
- 52. Activity: To investigate reflection •Place mirror on white paper. • Shine a ray into the mirror at an angle. • Note the position of the reflected ray. • Change the angle at that the ray makes by moving the light box. Ray box Mirror
- 53. The periscope Two mirrors parallelto each other at 450
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- 56. Concave mirror Concave mirorscan 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
- 58. Convex mirrors • Alwaysproduce an image that is right way up and diminished. • They are used seeing around corners and in shops for security.
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- 60. To investigate refraction •Shine a ray of light through a glass block at an angle. • Look at the ray of light in the glass from above. • Increase the angle between the glass and the ray box. • What do you notice?
- 61. Why does refractionoccur?
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- 63. To investigate refrationin a liquid
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- 66. Explore how objectsmay be magnified using simple lens or magnifier
- 67. Lenses opperate dueto refraction
- 68. Use of lenses •Camera • Telescope • Binoculars • Glasses • Microscopes
- 69. The telescope • Twoconvex lenses, the objective and the eyepiece. • Eyepiece has a short focal length • Objective has a long focal length • Object to be observed at least 10 m away. • Telescope has to be focused by varying distance between lenses (sum of focal lengths) • Magnification is the ratio of focal lengths
- 70. Be aware ofthe dangers of excessive sunlight dangers of looking directly at the sun effect of the sun’s rays on skin •Sunlight contains ultra-violet (UV)light. •If sunlight enters the eye it will kill the cells of the retina. These will not grow back. •. UV light on the skin causes sunburn and aging of the skin and may caues skin cancer. •Suncream absorbs UV light
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- 72. D esign andmake model telescopes Tubing Plastic wrap
- 73. Appreciate the importanceof sight The iris controlls the amount of light entering the eye Bright Dark
- 74. Structure of theeye The lense of the eye focuses light onto the retina which is carried to the brain via the optic nerve
- 75. Understand the roleof sunlight in photosynthesis • Plants make their own food using sunlight in a process called photosnthesis. • Without light plants cannot grow. • We eat plants for food or we eat animals/ animal products that have eaten plants.
- 76. Why the Moonseems 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
- 77. Waxing crescent This iswhat the Moon looks like from Earth Why the Moon seems to change
- 78. Last quarter This iswhat the Moon looks like from Earth Why the Moon seems to change
- 79. Waxing gibbous This iswhat the Moon looks like from Earth Why the Moon seems to change
- 80. Full Moon This iswhat the Moon looks like from Earth Why the Moon seems to change
- 81. Waning gibbous This iswhat the Moon looks like from Earth Why the Moon seems to change
- 82. Waning crescent This iswhat the Moon looks like from Earth Why the Moon seems to change
- 83. To demonstrate whythe shape of the Moon changes
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- 86. It is VERY DANGEROUSto look DIRECTLY at the Sun or at a REFLECTION of the Sun – it could make you BLIND
- 87. Infants and JuniorClasses (Teacher guidelines) • Identify different light sources • Explore the effect of light on materials • Identify materials that are transparent or opaque. • Experiment with shadows and reflections
- 88. Middle and seniorclasses (Teacher guidelines) • Distinguish between natural and artificial sources of light. • Explore that white light is made up of many different colours. • Investigate how light rays change direction as they pass through water and learn that this process is called refraction. • Understand that mirrors and other shiney surfaces can change the direction of light. • Explore how lenses are used to make things look bigger and smaller.
- 89. Science Curriculum. Infant andJunior Classes
- 90. Science Curriculum. First andsecond classes
- 91. Science Curriculum. Third andfourth classes
- 92. Science Curriculum. Fifth andsixth classes