MAKING A PINHOLE CAMERA

Patricia Willett, Designs For Learning Differences
Albuquerque, NM

Appropriate for grades 2-4.

OVERVIEW:  Imagine reaching for something that is visible in front
of you and not finding it there, or shining a flashlight in the
darkness and having it illuminate only something in back of you. 
This, of course, is not likely to happen, since light travels in
straight lines.  It is true that a beam of light can "bend" under
certain conditions, such as when going from air into water or
glass, and the reverse.  Scientists now know that light passing
through space is attracted and curved by the gravitational fields
of massive objects in space.  Other than these exceptions,
though, light does appear to travel in straight lines.  This
property makes many interesting things take place.

The pinhole camera demonstrates this property in an interesting
way.  Light shines through a narrow pinhole in the cereal box end. 
At the other end, an inverted image appears on wax paper taped
over the opening.  Why?  The drawing below suggests paper
an answer. If light travels in straight lines, the light going
from spot one on the left can only go to spot one on the right,
and so on.

PURPOSE:  The purpose of this activity is to introduce students to
a basic property of light and how we use this property in our
everyday lives.

OBJECTIVES:  Students will be able to understand how the image is
inverted--because light travels in straight lines.

ACTIVITIES:  

 1.  Punch a hole in the center of the box using the pin.

 2.  Remove the box top.  Put wax paper over the box's open end to
     make the screen.  Use a rubber band to hold it.

 3.  Point the camera at brightly lit objects in or outside a
     darkroom.  What do you see on the wax paper screen?

The observer's eyes will need to be about 30 centimeters away from
the screen to see a sharp image.  To use the camera in a lighted
place, you must shield the from light.  Roll black paper into a
large tube and fit it around the screen end of the box.  Press
your face against the paper shield's open end to images on the
screen.

Other Activities:

 1.  How must you move the camera to do these things?

     a.  To make the image move right?  Left?  Up?  Down?
     b.  To make the image get smaller?  Larger?

     What happens if the camera is still and the image moves?

 2.  How can you make a brighter, sharper image appear on the
     screen?  What would
     happen to the image if you:

     a.  Change the pinhole size?
     b.  Line the inside of the box with black paper?  White
         paper?
     c.  Use a longer or larger box or a shoebox?
     d.  Use paper other than wax paper for the screen?

RESOURCES/MATERIALS NEEDED:  

     Salt or oatmeal box                  Rubber band
     Sticky tape                          Wax paper
     Pin                                  Scissors
     Black paper

Your local library is an excellent resource for more information
on light and its properties.  

TYING IT ALL TOGETHER:  Make the drawing illustrated on the front
page on the chalkboard, except leave out the arrows.  See if the
students can draw the arrows in.  If they cannot, draw the arrows
in for them and let the students explain what happens.

If you wish to extend this activity further, invite a professional
photographer to bring his camera and talk about how the images the
camera receives are recorded on film.

Retrieved on April 29th from http://www.col-ed.org./cur/sci/sci01.txt.