Sources of Light


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Sources of Light

  1. 1. LIGHT ! from bonfires to lasers
  2. 2. Sources of light <ul><li>Hot objects give out light. </li></ul>A bonfire
  3. 3. The Sun <ul><li>Sunset in Venice </li></ul>
  4. 4. Stars <ul><li>Stars and galaxies give out light. </li></ul>Picture: Liverpool Telescope
  5. 5. Lightning
  6. 6. A worm living in dark caves sends out light from its tail. <ul><li>Liquid droplets form a string of shining beads to attract insects. </li></ul>tail of worm
  7. 7. Some cold things give out light: <ul><li>some fungi </li></ul><ul><li>glow worms </li></ul><ul><li>light sticks </li></ul><ul><li>LEDs </li></ul><ul><li>‘glow-in-the-dark’ stickers </li></ul>
  8. 8. How do we see light sources? <ul><li>Light travels from a source to our eyes. </li></ul><ul><li>We can see sources in a dark room. </li></ul>
  9. 9. Can we see in the dark? <ul><li>If there is no light </li></ul><ul><ul><li>we cannot see anything! </li></ul></ul><ul><li>Let’s try a test– </li></ul><ul><ul><li>Put a few small objects into the black bag----- </li></ul></ul>
  10. 10. How do we see things that are not sources of light? <ul><li>Light bounces off </li></ul><ul><li>and some reaches our eyes. </li></ul>
  11. 11. On the look out ! <ul><li>How do you know that the baby squirrel watches as it feeds? </li></ul>
  12. 12. Reflection <ul><li>When light bounces off something </li></ul><ul><ul><li>we say the light is reflected . </li></ul></ul><ul><li>We can try this with </li></ul><ul><ul><li>rough surfaces </li></ul></ul><ul><ul><li>and shiny surfaces. </li></ul></ul>
  13. 14. Shiny surfaces <ul><li>Light is reflected as a beam and can be seen on the wall. </li></ul>mirror wall
  14. 15. Move the mirror <ul><li>The light reaches a different place on the wall. </li></ul>wall
  15. 16. Look in a mirror <ul><li>Light is reflected. </li></ul><ul><li>You can see a reflection. </li></ul>
  16. 17. Change the direction of the light beam <ul><li>Light is still reflected. </li></ul><ul><li>You see a reflection </li></ul><ul><li> - in a different </li></ul><ul><li> direction. </li></ul>
  17. 18. Multiple reflections <ul><li>The lamp hangs between two large mirrors on opposite walls. </li></ul><ul><li>The reflection in the first mirror is reflected in the second mirror, which is reflected again in the first mirror - - - </li></ul>
  18. 19. Now for some games !
  19. 20. Colour
  20. 21. Sunlight shining on CDs <ul><li>Where do the colours come from? </li></ul>
  21. 22. Rainbow <ul><li>red </li></ul><ul><li>orange </li></ul><ul><li>yellow </li></ul><ul><li>green </li></ul><ul><li>blue </li></ul><ul><li>indigo </li></ul><ul><li>violet </li></ul>
  22. 23. Colours <ul><li>White light is made up of lots of colours </li></ul>
  23. 24. Colours from white light <ul><li>Look at a lamp through the grating. </li></ul><ul><li>You will see colours. </li></ul>
  24. 25. <ul><li>red </li></ul>
  25. 27. <ul><li>blue </li></ul>
  26. 28. Adding colours with light <ul><li>This is different to adding paints </li></ul>
  27. 29. Red + Blue  magenta
  28. 30. Blue + Green <ul><li>  cyan </li></ul>
  29. 31. Green + Red <ul><li> yellow </li></ul>
  30. 33. <ul><li>yellow </li></ul>
  31. 34. magenta
  32. 35. cyan
  33. 36. Fairy lights
  34. 37. Uses <ul><li>Lasers- produce very bright beams of light. </li></ul><ul><ul><li>The atoms all give out their light together </li></ul></ul><ul><li>CDs use laser light </li></ul><ul><ul><li>and reflection- </li></ul></ul>
  35. 38. CDs <ul><li>The surface has tiny pits and smooth bits </li></ul><ul><ul><li>in a spiral pattern </li></ul></ul><ul><li>the pits scatter light from a laser </li></ul><ul><li>the smooth bits reflect the light </li></ul><ul><li>so a coded message is read. </li></ul>spiral
  36. 39. Laser show <ul><li>Physics is in everything </li></ul>