Refraction Inquiry. Background information: Refraction when a waves moves from one medium to another medium at an angle and changes speed.

Transcription

1 Refraction Inquiry Direction: Copy down the purpose, background information and answer all the questions on notebook paper. Remember to put part of the question into your answers. Purpose: How does light interact with transparent objects. Background information: Refraction when a waves moves from one medium to another medium at an angle and changes speed. Introduction: Have you looked though a window today? For that matter, did you observe your hands while washing them this morning? Did you look at your juice through the side of a glass during breakfast? If you did, you observed light passing from one transparent material to another. What happens when light strikes a transparent object or materials like a window or the surface of water? You may already have some ideas. Here are a few questions you can ask yourself: Does all light that strikes a transparent object enter it? Does light entering a transparent object travel in a straight line all the way through it? Does the light entering a transparent object leave it? Does the composition or shape of a transparent object affect the behavior of light? In this inquiry you will conduct four mini experiments to see how light interacts with different transparent objects. Each experiment will be at a different lab station. You will rotate to the different lab station when instructed by the teacher. It does not matter where you start, so wait until the teacher tells you to rotate.

2 Part I: Rising Coin 1. Put the coin in the bowl. 2. Walk backwards until you cannot see the coin in the bowl. 3. Draw a what you see. 4. Have someone slowly pour water into the bowl. 5. Carefully watch the bowl from where you are standing until the bowl if filled with water. 6. Switch roles and do this so that everyone gets a turn observing the coin. 7. Discuss what you observed as a group. 8. Draw what you saw as the water began to fill the bowl using the boxes below. before pouring during pouring after pouring a. Why did this happen? 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.

3 Part II: Bending Pencil 1. Place the pencil in the beaker without water. 2. Look at the beaker at eye level. 3. Draw what you see. 4. Place the pencil in the beaker with water. 5. Look at the beaker at eye level. 6. Draw what you see. 7. Slowly begin to stir the pencil around in the beaker with water. a. What do you see when you are looking at the beaker at eye level? b. What is the difference between the two drawings? c. Why did this happen? Straight or bent: What happens when you look at the pencil through the side of the glass? Light plays 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!

4 Part III: Turning Arrow 1. Use the index card with the arrow drawn on it. 2. Place the card directly behind the beaker filled with water. (really close to the beaker). 3. Move to eye level with the arrow. 4. Draw what you observe. 5. Move the arrow back slowly from the beaker of water. 6. Draw a after picture detailing what you observed. Before After a. Why do you think this happened? 7. Try placing the other objects very close to the beaker. b. Write down some observations that you notice with your group. 8. Try placing the other picture close and far away. c. Write down some additional observations that you noticed with your group. d. Why did this happen? 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.

5 Part IV: Magnification Experiments 1. Using the newspaper clipping, draw your observations as you look at the newspaper through each of the 3 different items. a. What did you see with your naked eye? b. What did you see looking through the magnifying glass? c. What caused the change in what you saw from using only your eye to the magnifying glass? d. What did you see as you looked through the drop of water on plastic? e. What caused the change from using your eye to the drop of water on the plastic image? f. Why did this happen? 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 because the underwater or under- glass object is being magnified.