Activities

Measuring Light Intensity

Your students can use a light meter in a manual camera to roughly measure light intensity in footcandles in different parts of your greenhouse. Here's how. First, set the film speed at ASA 200 and the shutter speed at 1/125 second. Aim the camera at a white sheet of paper in the greenhouse. Get close enough so the meter records only the light reflected from the paper (be careful not to create shadows). Focus on the paper and adjust the f-stop until a correct exposure shows in the light meter of the camera. F-stops will equal approximate footcandles as follows:

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