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?
