A pin-prick as spy-hole - Xplora

S C I E N C E C E N T E R
o p s c h o o l
A PIN-PRICK AS SPY-HOLE
Who wants to be seen when they are spying? A newspaper with a hole in
is a bit obvious don’t you think? How about a box with a hole the size
of a pin-prick? Will it show you what’s around you? That’s what you are
going to fi nd out with this exhibit: the ‘camera obscura’, a forerunner of
the camera. Do you see anything?
Materials:
WHAT DO YOU NEED?
Big cardboard box (at least 50 x 50
centimeters)
Large sheet of white paper
Masking tape
Aluminum foil
Gaffer tape
Glue
Black pullover / towel
BUILDING PLAN
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Tools:
Pencil
Ruler
Awl
Scissors
Thumbtack
Compasses
Before he starts building, a builder of exhibits fi rst makes a building plan of the exhibit.
That’s what you are going to do too. A building plan shows how something is made and
how big it will be.
First look at the drawing of the ‘camera obscura’. This will give you an idea of what the
exhibit will look like and how it should be
constructed. Tips: 1. You can read the text
accompanying the drawings already. 2. If
the materials for your exhibit are already
available, it’s a good idea to have a look at
them too.
Under ‘What do you need?’ you can see all
the materials and tools that you need. But
the list of materials does not show exactly
how much of them you will need. You will
know that only when you have decided how
big the exhibit will be. So fi rst decide with
your pal how big the exhibit should be and
how you are going to draw it.
Discuss your plan with your teacher.
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Now use a pencil and ruler to make a building plan in your workbook. You both make
your own building plan in your workbooks, but you do it in the same way. You make
the drawing to scale 1:2. This means that one centimeter in the drawing is really two
centimeters in real life. So if your real cardboard box is fi fty centimeters high, it is
twenty-fi ve centimeters high in the drawing. Write the real measurements next to the
different parts. In your building plan, you should also mark where holes should be in the
box. For this, use the description under ‘How are you going to make it?’
You are going to show the building plan to the rest of your class. Tell them how you
plan to build the exhibit. Ask the other children and the teacher what they think of the
building plan. Maybe they have an idea to make it even better.
Show your improved building plan to the teacher. When he or she has approved your
drawing, you can start making the list of materials together.
LIST OF MATERIALS
The building plan is ready, so you now know the size of all the materials and you can
count how many of each part you need. Make the list of materials in your workbook and
give the list to your teacher. Ask him or her where you can get these things. Then you
can really start building!
HOW ARE YOU GOING TO MAKE IT?
To build an exhibit together you have to discuss a lot and make agreements. How are you
going to tackle it? Who does what?
Divide up the different tasks as fairly as possible.
Try to work together as much as possible, so that you both get some experience of
building. If you come across a diffi cult word, look it up in a dictionary.
1.
Take a good look at the drawing on the previous page. We will call the side of the box in which
you stick your head the bottom. The side of the box that is behind your head in the drawing is
the back. The side that your head faces is the front.
2.
Take the cardboard box. Decide which sides will be the bottom, front and back. Seal the bottom of
the box with tape.
3.
Start by making holes in the box. At the back of the bottom of the box, cut out a hole with the
scissors. Make the hole big enough for your head to just fi t through. Take a good look at the
drawing to see how you should make the hole.
Fix gaffer tape around the edge of the hole so that it does not tear.
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4.
Make a round hole in the middle of the upper
side of the back of the box. First draw this
hole with compasses. The circle must have
a diameter of 3 centimeters and start 10
centimeters under the upper edge of the box.
Then prick out the circle with the awl.
5.
Cut out a piece of aluminum foil that is slightly
bigger than the circle. Fix it over the circle with
masking tape on the outside of the box.
6.
Glue a large sheet of white paper to the inside
of the front of the box.
Make sure that the whole side is covered with
white paper. Use more than one sheet if you
need to.
7.
Seal the top of the box. Now put the box on
your head. Inspect the corners and seams of the
box. Is there light coming in anywhere? If so,
stick gaffer tape over the place on the inside of
the box.
Don’t worry about the light that comes into the
box around your neck.
8.
Now use a thumbtack to prick a small hole in
the middle of the aluminum foil.
9.
Decorate the outside of the camera obscura.
Make it look attractive!
HOW DOES IT WORK?
The exhibit is ready. It works best outside because there is a lot of light there. It works as
follows. Stand with your back to the sun and stick your head through the opening in the
bottom. Make sure that you are looking towards the white paper (the screen).
Wrap the black pullover or a towel around your neck so that no light enters the box
through the hole in the bottom. Give your eyes time to get used to the dark. Then look
carefully at the screen. What do you see?
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WHAT DO YOU SEE HAPPENING?
Now look for the science behind the exhibit. This exhibit is about the camera obscura. Do
the research below. Write the answers in your workbook under ‘Research report 1’.
1.
Go outside and place the exhibit on your head. You should see the things around you on the
screen. Take another good look. Do you see them the right way round or upside down? Are they
mirrored or not? Walk around a bit and see how the pictures change.
2.
See if you can see two objects around you (one of which is further away than the other) at the
same time on the screen. Which is bigger? Are they both as clear on the screen or is one object
clearer than the other?
Now make the hole in the aluminum foil bigger with the point of a pencil. Press the pencil into
the aluminum up to half of the diameter of the pencil.
Now see if you can still see two objects around you at the same time. What do you see now?
Compare this with what you saw through the small hole.
N.B. If you want to have a small hole again, you can replace the aluminum with a new piece.
Make a new hole in the foil with a thumbtack.
WHAT’S THE ANSWER?
Now you are going to fi nd information about the camera obscura. You can look for
information in the school media library, the library or the Internet.
Go to www.sciencecenteropschool.nl and then to ‘primary school pupils’ and click on ‘links’.
Under the title of your exhibit, you will fi nd a number of websites with background
information.
Answer the questions below and write the answers in your workbook under ‘Research
report 2’.
Operation / Science:
Why can you see the things around you in a camera obscura? How does the light go through the
little hole? How do you see the image on the inside of the box?
Invention:
Who invented the name ‘camera obscura’? When was that? Was this person also the inventor of
the camera obscura?
Application:
A camera uses the same principle as the camera obscura. What are the similarities and differences
between a camera obscura and a camera?
Let your teacher read your answers.
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A pin-prick as spy-hole