A simple procedure is presented for estimating the focal length of a concave lens using only a meterstick and a lined drawing. Care must be taken to avoid confusing the magnification of a lens with the magnifying power. The results of such confusion are demonstrated.

This content is only available via PDF.
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.