Patricia Willett, Designs For Learning Differences Albuquerque, NM MAKING A PINHOLE CAMERA 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.
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