This page includes 4 tasks which can be used as mini plenaries through out a lesson on lenses.
1. students identify lenses in everyday uses
2. students try to describe a lens (suggestion: the teacher may give some hints and give the definition afterwords so that the students can mark themselves)
3. students identify the main key terms on a lens
4. after a short practical (moving lenses and observing the changes of the image), students may conclude about the main factors affecting the focal length and the magnification