Activity 4    F Box Lab Setups

The F-Box, trio of lenses, masks, and projection screens demonstrate the inter-relationships of focal length, image size, aperture, and image brightness.  Record all your data - image sizes, focal lengths, brightness with and without the aperture masks, then work together with others to create a concept map to show how the attributes of images depend on the properties of the lenses.

Place the projection screens at the best focus for each lens in the trio.

What is different about each lens to cause the focal lengths to vary?

Demonstrate the effect when aperture is limited. Place a mask over the lenses; the mask attaches with Velcro.

 
Notice how the mask covers the outside part of the each of the lenses, reducing the aperture. What happens to the size and/or brightness of each lens when the aperture is reduced?

High school students attending NASA's Saturday Academy for Space Science at Chicago State University also conducted these investigations. See webpage: http://www.handsonuniverse.org/activities/Explorations/sass/module2.html.