Bending Pencil Experiment

Transcription

1 Bending Pencil Experiment Place the pencil in the cup without water. Look at the cup at eye level. Draw what you see. Place the pencil in the cup with water. Look at the cup at eye level. Draw what you see. What is the difference between the two drawings? Now, slowly begin to stir the pencil around in the cup. When looking at the cup at eye level, what do you see? Draw your observations of three different things you see in the cup while you stir.

2 Turning Arrow Experiment On an index card, draw an arrow. Place the card behind a clear cup filled with water. What do you observe? Draw a before and after picture detailing what you observed. Before (not behind cup) After (behind the cup) Why do you think this happened? Other experiments to conduct: Try drawing other objects. Try placing them very close to the cup. Try placing them very far away from the cup. Try something else you can think of. Note some of your observations:

3 Magnification Experiments Using the newspaper clipping, draw your observations and you look at it through: Your naked eye Magnifying Glass Drop of water on plastic Glass bead What did you observe as you looked through each object?

4 Rising Coin Experiment Do the following steps at your station: 1. Put the coin in the bowl. 2. Walk backwards until you cannot see the coin in the bowl any more. 3. Have someone pour water slowly into the bowl. 4. Watch the bowl from where you are standing. What did you observe? Draw what happened as the water began to fill the bowl.

5 Listed below is the REASON that each experiment works. It is the scientific rationale if you will. Rising Coin We see that when the bowl is empty, the edge of the bowl stops you seeing the coin. When the bowl is full, the light bends over the edge, so you can see the coin. We notice that things at the bottom of a pool or river always look closer to the surface than they really are. This is because of the way light is bent through water and is an effect of refracted light. Bending Pencil Straight or bent? What happens when you look at the pencil through the side of the glass? Light play tricks on your eyes. The pencil looks bent. This is because light travels slower through water than through air. As the light enters the glass of water it slows down(changes direction) and as it leaves the glass it speeds up again therefore making the pencil look bent! Magnification Experiment When light moves through different mediums, it changes shape. When you look at the newspaper through the glass or water, the light had to pass from air through the new medium. Looking from above, an object under this new medium appears larger than it does in air. It's not that the image the light gave our eyes is bigger. It's that the image is actually closer to our eyes, since the light is not passing straight down, but is instead bending relative to the water's surface. Light passing straight down would be perpendicular to the water's surface, like the vertical line on the letter T. A closer image looks bigger--the underwater or under-glass object is magnified. Turning Arrow Just as with the pencil bending, the light is playing tricks on your eyes. The arrow looks as though it has turned because the light is passing twice through the different mediums (air to glass back to air back to glass to air to your eye). This is because light travels slower through water than through air. As the light enters the glass of water it slows down(changes direction) and as it leaves the glass it speeds up again therefore making the arrow look as though it has turned.