Pinhole Camera Lab
The pinhole camera is a simple application of the rectilinear propagation of light. It consists of an opaque box with a pinhole at one end and a translucent screen at the other end. If the pinhole is pointed at a bright object, an image forms on the translucent screen.
Purpose: To allow students to predict, observe and explain the important light property of rectilinear propagation.
Materials: Pinhole camera
Candles
Light bulb
Darkened room
Hypothesis: Assume that light travels in a straight line, use the diagram below to predict the image characteristics for the light source. This is done by imagining light travelling from the top of the candle flame (A) and the bottom of the candle flame (B).
Predicted Image Characteristics:
Size (smaller / same size / larger) ______
Attitude (right side up / upside down) ______
If light doesn’t travel in a straight line, what would be your predictions?
Predicted Image Characteristics:
Size (smaller / same size / larger) ______
Attitude (right side up / upside down) ______
Questions:
1) What differences do you expect to see if light travels in a straight line vs. if light doesn’t?
2) What makes you believe your predictions are correct?
Observations:
Now collect a pinhole camera for your group and test your observations by viewing a candle and drawing what you see.
Predicted Image Characteristics:
Size (smaller / same size / larger) ______
Attitude (right side up / upside down) ______
Change the distance between the pinhole camera and the light source. What happens to the image formed when the distance changes? ______
______
______
Record what the candle looks like…
-with your eyes -on the pinhole screen
Analysis:
1) How do your predictions compare with your observations? What problems were there with your predictions and what led you to make those predictions?
2) What happens to the size of the image as you change the distance to the light source?
3) Describe the characteristics of an image that you would now expect to see if you looked at a light source through a pinhole camera. Why would you expect to see it that way?
4) What type of image would you expect to see if the pinhole was as large, or larger, than the source of light? Show with a diagram. (Draw below)
5) A regular camera has a large opening to let in more light than a pinhole. How is the camera equipped to overcome the problem that occurs when the opening is larger than a pinhole?