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#1213. Camera Obscura

other, level: Middle
Posted Wed Jul 28 07:12:33 PDT 1999 by Joe McDonald (sawdust107@yahoo.com).
NAHS, Montgomery County, PA
Materials Required: See Lesson Text
Activity Time: 2 days
Concepts Taught: Reflected Light & Inverted Images

The "Camera Obscura" and its' present day cousin, the "Pinhole Camera" represent the earliest attempts by man to permanently record a realistic image. A camera obscura can be as large as a room or as small as a salt box.

After completion of this 2 day activity, the students will have an understanding of how reflected light forms an image and be able to describe why the image is upside down.

Materials:

Two paper towel tubes -- one should be slightly smaller than the other and fit into the larger one.

3" square piece of aluminum pie plate (soda cans work)

3" square piece of waxed paper or frosted acetate.

rubber band - tape - #10 sewing needle -- black marker- black poster paint

Procedure:

1. Paint the outside of the smaller tube black in order to subdue any stray light. This step is optional but can improve the quality of the finished camera obscura.

2. Locate the center of the 3" piece of aluminum and poke a hole in it with the #10 sewing needle. You will get better results if you rotate the needle as you push. Push part way through from one side and complete the operation from the other side.

3. Use the black marker to blacken one side of the aluminum. Be careful to not clog the hole with ink from the marker.

4. Trim the aluminum so that is round and the same approximate diameter of the larger tube. Be careful to keep the pinhole in the middle as you trim.

5. Tape the aluminum to the end of the larger tube. Color the tape black with your marker to prevent light from entering around the edges of the aluminum.

6. Use the rubber band or tape to secure the waxed paper or acetate to the end of the smaller tube. Make sure to keep the material drawn as tighly as possible over the end of the tube as you fasten it.

7. Place the smaller tube into the larger one waxed paper end first.

8. Go into a brightly lit area (outside works best), and put the open end of the tube up to your eye.

After your eye adjusts to the image:

1. How does the image appear to you?

2. Why?

3. What happens as you move the waxed paper closer to, or farther away from, the pinhole.

4. Why?

As a follow-up activity to making a camera obscura, you might want to consider making and taking pictures with a pinhole camera.

Some Internet Sites For Exploration:

Camera Obscura
http://www.nmsi.ac.uk/nmpft/collections/gen14.html

Pinhole Camera "did you know"
http://learningedge.sympatico.ca/recess/g@w/ssbuild/pastproj2/pastproj2a.html