Light & Sound, Light Reflection Relay
Summary
In this activity, students will investigate how light reflects off smooth surfaces (mirrors), learn about angles of reflection, and apply that knowledge in a relay experiment where they must direct a light beam around the room by reflecting it off 3 mirrors to hit a target placed in the classroom. Each group will investigate different paths and angles of reflection to hit a target. Once they have found a viable solution, they need to demonstrate their success to the teacher. Teachers will record observations throughout this exploration, documenting student progress in the groups and recording when each group has found a successful solution. Each group is required to complete one relay, but may continue hitting other relay targets as time allows.
Learning Goals
Context for Use
Description and Teaching Materials
Materials per student group
Laser light - pen lights work well
3 hand held mirrors, about 3" x 5" or larger
One target taped to the wall in the classroom - may be bull's eye or other object on a 8.5 x 11 sheet of paper
Before this lesson, you will need to hang targets on the wall. You will also need to mark starting spots in the classroom. You need enough targets and starting positions for each group. You may wish to label starting positions and targets specifically for each group.
Students should have a prior understanding of how light travels.
* Discuss how light waves behave when they strike a smooth surface. They will bounce or reflect.
* Demonstrate how a laser light (which travels in a straight line without spreading out like other light sources) reflects off a mirror.
* Have students move into groups to investigate how laser light reflects. They should discover how to point the beam in a certain direction. Have them try to hit a target using one mirror.
* Gather students back to a large group. Ask students to share what they discovered. Discuss angle of incidence and reflection - the light beam will reflect at the same (equal) angle that it hits the mirror.
* Direct students back to groups. Students need to put one person with the laser light on the starting position (spot marked in classroom). The others will each have a mirror. Students will shine the light on the mirrors, reflecting to the next mirror and the next, aiming for the target. The light must bounce off all 3 mirrors and hit their designated target. Furniture in the room should not be moved. Students should not climb on furniture; they must work around it.
* Once students have a valid path, they need to demonstrate this for the teacher. Multiple paths are possible.
* Groups may try to hit more than one target as class time allows.
* Gather students together as a class to share working strategies before end of lesson.
Adapted from http://www.iit.edu/~smile/ph91ld.html
and http://scienceolympiad.kulbago.com/Reflection%20Relay%202009.pdf