This four-lesson "legacy cycle" unit for middle school, science and technology classes is structured with a contextually-based Grand Challenge followed by a sequence of instruction in which students first offer initial predictions (Generate Ideas) and then gather information from multiple sources (Multiple Perspectives). This is followed by Research and Revise as students integrate and extend their knowledge through a variety of learning activities. The cycle concludes with formative (Test Your Mettle) and summative (Go Public) assessments that lead students towards answering the Challenge question. See below for the progression of the legacy cycle through the unit. Research and ideas behind this way of learning may be found in How People Learn, (Bransford, Brown & Cocking, National Academy Press, 2000); see the entire text at http://www.nap.edu/html/howpeople1/.

The "legacy cycle" is similar to the "engineering design process" in that they both involve identifying an existing societal need, combining science and math to develop solutions, and using the research conclusions to design a clear, conceived solution to the original challenge. Though the engineering design process and the legacy cycle depend on correct and accurate solutions, each focuses particularly on how the solution is devised and presented. See an overview of the engineering design process at http://en.wikipedia.org/wiki/Engineering_design_process.

In lesson 1, students are prompted to answer a Grand Challenge (see the Summary section). They begin by Generating Ideas in the associated activity, and answering questions such as, "What background knowledge is needed?" and "What do you know about security systems already?" Students then enter the Multiple Perspectives phase of the legacy cycle by watching a clip from the Discovery Channel's Mythbuster's Crimes and Myth-Demeanors episode.

In lesson 2, students enter the Research and Revise step focusing on the properties of light. After an introduction to the electromagnetic spectrum, they focus on the properties of visible light with respect to both the particle theory and wave theory. Students also develop an understanding of constructive and destructive waves as well as reflection and refraction. In the associated activity, they explore reflection, absorption and transmission with respect to everyday objects. In addition, students explore refraction by creating a rainbow in the classroom.

During lesson 3, students continue in the Research and Revise phase of the legacy cycle for further learning. They focus on how a laser functions and how light properties enable this device. In an associated activity, students research the types of lasers and present their findings to the class. After this lesson, students possess the knowledge required to solve the challenge question.

Lesson 4 includes an associated activity in which students enter the Test Your Mettle phase of the legacy cycle as well as in-class time to prepare the final Go Public presentation. Just prior to going public with their solution, students build a model system replicating the design they believe to be the best. This design, as well as individual assessment questions, tests their understanding of the laser light properties. To conclude, student teams make informative class presentations on their final security system designs. These presentations test students' abilities to apply the properties of light that they have studied throughout the unit.

Lesson 4 includes the final Go Public phase of the legacy cycle in which students are prompted to apply the concepts they have learned to answer the Grand Challenge question. In this phase, students relate the learned concepts on light properties to designing a laser security system, which serves as a cumulative assessment covering the previous three lessons.

This unit also meets the following Tennessee Foundations of Technology educational technology content standards: 2.0, 3.0, 4.0, 5.0, 6.0, 7.0 and 8.0; see http://www.state.tn.us/education/cte/.

This unit also meets the following National Science Education Standards (NSES) teaching standards: A, B, C, D, E, F; see http://www.nap.edu/readingroom/books/nses/.