Demos: 7A-04 Plane Mirror "Levitation"

By making use of the apparent L to R reversal in a plane mirror, the instructor appears to levitate, i.e. appears to have both legs in the air simultaneously.

Directions: The large plane mirror is placed on the lecture desk facing the students. Stand straddling the mirror near the far edge. Your right leg is now behind the mirror, out of view, so that when you lift your left leg, it appears that your right leg lifts also. Hint: When lifting your left leg, move it away from the mirror a bit. This allows the students to see the reflection better.

Suggestions for Presentation: You can play this one to the hilt! One way is to start flapping your arms slowly, then as you flap them faster and faster, slowly lift your left leg. Even more dramatic (and perhaps more humorous) is to fold a poster board around each arm and tape the sides together so that you have what looks something like an air foil. Ask the lec-demo technician (or perhaps a student) to use the large air blower to direct a stream of air at you, creating a “lift.”

Point out that the reflection of the left leg is reversed front-to-back, so that the inversion causes the left leg to look like a right leg.

Applications:

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