In this activity, students test the Law of Reflection based on experimental evidence.However, the back-silvered glass mirrors present a twist. As light travels from air into glass, it changes direction (refracts), reflects off the shiny metal back coating, then changes direction again upon emerging from the glass. The reflected ray may not match up with students' expectations, and offers them a challenge to work out what happened as the light traveled into and out of the mirror. Mirrors are everywhere: in our cars, bathrooms, shiny metal surfaces, water, and windows. Large astronomical telescopes use curved mirrors (rigid glass or polymer coated with a metal) to focus star light on to electronic detectors.

What Students Do

Students produce raw data and explanations based on their data. Their raw data are their pencil tracings of incident and reflection rays.

Materials You Will Need

For each student team

• pen and pencil
• Laser pointer (Scientific Laser Connection)
• 2 Binder clips (office supply store)
• 1 Flat back-silvered mirror, 1/4 inch thick (Wal-Mart, Target)
• Letter size (8.5 x 11 inches) graph paper
• 1 Protractor