Blue sky – red sunset

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Science Experiment on the Sky

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Blue sky – red sunset

  1. 1. Blue sky – Red sunset Yu Weiran(33) 1A3
  2. 2. Aim <ul><li>When the sky is not cloudy, it is blue in colour. </li></ul><ul><li>When the sun is setting, it is red. </li></ul><ul><li>Why is this so? </li></ul>
  3. 3. Equipments <ul><li>A flashlight </li></ul><ul><li>A transparent container with parallel sides </li></ul><ul><li>250ml of milk </li></ul>
  4. 4. Steps <ul><li>Set the container on a table where you can view it from all sides. </li></ul><ul><li>Fill the container to quarter full. </li></ul><ul><li>Light the flashlight and hold it against the side of the container so its beam shines through the water. </li></ul><ul><li>Try to see the beam as it shines through the water. (It is not easy) </li></ul>
  5. 5. Steps <ul><li>Add about 60 millilitres of milk to the water and stir it. </li></ul><ul><li>Hold the flashlight to the side of the container, as before. </li></ul><ul><li>Notice that the beam of light is now easily visible as it passes through the water. </li></ul><ul><li>Then, add the rest of the milk. </li></ul><ul><li>You will realise that the beam of light have became blue. </li></ul>
  6. 6. Pictures of the experiment Start
  7. 7. Different views of the setup
  8. 8. Why is this so? <ul><li>When the beam of a flashlight travels through air, we cannot see the beam from the side because the air is uniform. (Light travels in a straight line) </li></ul>
  9. 9. Why is this so? <ul><li>When milk is added into water, more particles are added into the water. </li></ul><ul><li>Milk contains many tiny particles of protein and fat suspended in water. </li></ul><ul><li>These particles scatter the light and make the beam of the flashlight visible from the side. </li></ul>
  10. 10. Colour of light <ul><li>Different colors of light are scattered by different amounts. </li></ul><ul><li>Blue light is scattered much more than orange or red light. </li></ul><ul><li>Because we see the scattered light from the side of the beam, and blue light is scattered more, the beam appears blue from the side. </li></ul><ul><li>Because the orange and red light is scattered less, more orange and red light travels in a straight line from the flashlight. </li></ul><ul><li>When you look directly into the beam of the flashlight, it looks orange or red. </li></ul>
  11. 11. Sunset and Clear Sky <ul><li>The light you see when you look at the sky is sunlight that is scattered by particles of dust in the atmosphere. </li></ul><ul><li>Looking at the sky is like looking at the flashlight beam from the side </li></ul><ul><li>When you look at the setting sun, it's like looking directly into the beam from the flashlight. </li></ul>
  12. 12. Sunset and Clear sky <ul><li>At sunset or sunrise, the sunlight we observe has traveled a longer path through the atmosphere than the sunlight we see at noon. </li></ul>
  13. 13. Experiment Adaption <ul><li>A Handbook for Teachers of Chemistry Volume 3 by Bassam Z. Shakhashiri </li></ul>

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