Air Lenses
Safety Warnings
Warning: Water and Electrical Safety
Purpose
Air-filled lenses submerged in water reverse the expected behavior: convex shapes diverge light and concave shapes converge it. Students see directly that lens action depends on the refractive index contrast between lens and medium, not shape alone.
Figure 1:
Complete apparatus: fiber optic lamp, condenser for collimating the beam, and aquarium on a wooden block.
Figure 2:
Convex air lens in water: the collimated beam diverges after passing through, opposite to a convex glass lens in air.
Figure 3:
Concave air lens in water: the collimated beam converges after passing through, opposite to a concave glass lens in air.
Figure 4:
The concave (left) and convex (right) air lenses used in this demonstration.
Equipment
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