World 1 · Reflection & Refraction · 6 minApparent Depth
Why pools look shallower
Teaching this? Open projector mode
Refraction bends light leaving the water, so submerged objects look closer to the surface than they really are. For viewing from air nearly along the surface normal, apparent depth ≈ real depth ÷ n.
A pool that is 2.0 m deep looks only about 1.5 m deep (2.0 ÷ 1.33). The same effect makes a straw in a glass appear bent and broken at the surface.
Check yourself
A stone rests 1.33 m under water (n=1.33). Viewed from air nearly straight down, its apparent depth is about…
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