Starting Point -- Tabletop Light Source Activity
Most people know
very little about what happens when light comes through a pinhole.
This activity provides an opportunity for teachers to experiment
with pinholes and see how they work. This early stage of inquiry,
sometimes called the "messing about", or exploratory stage, is
what we are calling an inquiry starting point. Pinholes are an
easily accessible, common phenomenon, and are a good starting point
for inquiry because they create dramatically visible effects. They
thus provide teachers with many opportunities to raise questions
and begin to piece together their observations and understandings.
40 - 60 minutes
Groups of 2 to 4
(for 24 to 32 people)
The darker you
can make the room, the better it will be for observations. Set
up each light source with (1) a bulb with a different filament
in each one, and (2) a piece of black construction paper or aluminum
foil over each of the four openings.
To Do and
activity by telling teachers that in their exploratory investigation
of pinholes they are free to go in whatever direction they like.
Start them working by asking them what they think they'll see if
they make a hole in the black paper covering the Tabletop Light
Source openings. Have them make one pinhole, then another. Are
they surprised by the shape of the light coming through?
express surprise, suggest that they make more holes and maneuver
the screen or revise the size of the hole to find out more information.
After a while, have them walk around and look at the patterns on
the other tables. Sometimes it takes about 20 minutes to adapt
to the dark and really see what is happening.
why they think the light patterns are different at each table.
There may be several reasons offered-with children there often
are. If so, each hypothesis can be used as the basis for a short
Ask them if the
patterns are the same from all four windows of the Tabletop Light
Source? What if they turn their light fixture at the top of the
further inquiry, you can pose these questions:
- what if you
change the shape of the pinhole?
- are some images
more fuzzy than others?
- can the image
be made bigger or smaller?
- can the image
be turned right-side up?
- what are the
images we see other than the filament?
The light patterns
on the table and the screen are images of the filament in the bulb,
and therefore are different for each of the different bulbs you
Patterns on different
sides of the same light source may be different because the image
coming through the pinhole at each window is of the filament from
a different orientation. A "c" shaped filament can have a "c",
or an "I" image projected through the pinholes.
If you replace
the clear bulb with a soft frosted bulb, teachers will see an image
of the whole light fixture and understand that the image is upside
For a more detailed
explanation, see Pinhole Images-What's Happening