Spherical Water Lens
Purpose
A water-filled spherical globe magnifies a suspended marble in air, but the magnification nearly vanishes when the globe is submerged in water. Students see directly that lensing power depends on refractive index contrast at boundaries, not just lens shape.
Figure 1:
Top: Water-filled globe magnifies the suspended marble compared to the reference marble on the lab jack. Bottom: Submerged in water, the globe loses most of its lensing power and the marble appears slightly smaller than the reference.
Demo Apparatus
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