# Teacher Investigations

A partial listing of the teacher investigations is contained here.

## Investigation L1: Light and Illumination

### Activity L1.4: What can a pinhole do?

(Demonstration/Laboratory)

Equipment: Frosted bulb in holder, cardboard or poster board about 10-12 cm on a side, nail with sharp point, translucent screen (tracing paper mounted on a cardboard frame), measuring stick, small ruler.

1. WHAT'S YOUR IDEA? Your instructor has a setup. What do you predict will be seen on the screen if the pinhole was placed between the source and the screen? Why do you think so? Write down your reasoning and draw a diagram.

2. WHAT ARE THE GROUP'S IDEAS? What ideas do other members of your group have, and what kind of diagrams have they drawn?

3. MAKING OBSERVATIONS: Poke a hole in your cardboard and set up your equipment like your instructor's. See what actually happens. Describe what you observe on your screen. Is this what you had predicted?

4. MAKING SENSE: How can you explain what you observe on the screen? Discuss this with the other members of your group and try to reach a consensus on an explanation. Summarize the explanation and draw a diagram.

5. WHAT'S YOUR IDEA? Make some predictions before actually doing the following. If you were to keep the distance between the bulb and pinhole constant, but then move the screen much closer to the pinhole, then much farther away, what would you observe on the screen? Write down your own predictions along with some diagrams.

6. WHAT ARE THE GROUP'S IDEAS? Compare your predictions and diagrams with those in your group. Include here those that differ from yours.

7. MAKING OBSERVATIONS: Try the experiment and describe what happens.

8. MAKING SENSE: If your observations are different from your predictions, discuss with your group members how you could explain your actual observations.

9. WHAT'S YOUR IDEA? Make another prediction. Suppose you were to make the hole in the cardboard larger and larger (and ultimately as large as the diameter of your thumb). What would you observe on the screen? Write down your own prediction and your reasoning.

10. WHAT ARE THE GROUP'S IDEAS? Discuss your prediction and reasoning with other members in the group. Summarize ideas that differ from yours.

11. MAKING OBSERVATIONS: Try the experiment. Make the hole larger in steps and describe what you observe.

12. MAKING SENSE: If the outcome of the experiment is different from your prediction, try to explain your actual observations. Why does the pattern change when the hole is made larger?

Be creative. Using whatever apparatus you can get a hold of, set up an arrangement where you can produce several pinhole patterns of illumination of various sizes on the screen. You may find it useful to share apparatus with a neighboring group. Draw sketches of your final arrangement and what is observed on the screen.

## Investigation L2: Reflection of Light

### Activity L2.4: How can you read a paper if it is hidden from your direct view?

(Laboratory Activity)

Equipment: file folder, paper.

1. WHAT'S YOUR IDEA? Suppose you drew some block letters on a square of paper about 5 cm on a side. With a visible barrier between you and the letters, can you think of a way that the letters could be seen and read in their normal way?

2. WHAT ARE YOUR GROUP'S IDEAS? Write down ideas that your group may have that are different from yours. Are all the ideas workable?

3. MAKING OBSERVATIONS: Draw the letters on the paper and lay the paper on the table. Set a file folder on end so that it blocks your direct view of the letters. Using the smallest number of mirrors and the smallest sized mirrors possible, set up a system so that you can read the letters in their proper orientation. Draw your sketch of the completed apparatus here. How many mirrors did you use?

4. MAKING SENSE: Write a commentary on how your device works. Could you get the same results using fewer or more mirrors? How many would you have to have? Explain.

## Investigation L5: Images That Cannot Be Formed on Screens

### Activity L5.1: Where are your eyes focusing when you look at your mirror image?

(Demonstration/Seat Activity)

Equipment: small mirror (per person if possible).

1. WHAT'S YOUR IDEA? Where are your eyes focusing when looking at your reflection in the mirror? Are your eyes focusing on the surface of the mirror, or somewhere else? What evidence do you have for your answer?

2. WHAT ARE YOUR GROUP'S IDEAS? Write down any ideas that are different from yours. Can you reach consensus?

3. MAKING OBSERVATIONS: Hold the mirror between your thumb and forefinger at arm's length and slowly bring the mirror toward your face, noting when the image of your face and your thumb against the mirror start to go out of focus. What did you observe? Did they go out of focus at the same time or different times? If different, which went out of focus first? What did other members of your group observe? Can you reach consensus?

4. MAKING SENSE: What does this observation suggest about where your eyes are focusing when looking at your mirror image? Compare your answer with those of your group. Are they the same? Can you reach consensus?