How do lenses in glasses and telescopes bend light to help us see?
Light's Gentle Turn
How do lenses in glasses and telescopes bend light to help us see?
Light travels in straight lines, like the world's most disciplined marcher. It never wanders, never daydreams, never takes a shortcut through the grass. But give light one little trick — a curved piece of glass — and suddenly it bends, just enough to help your eyes do something they couldn't do alone.
Here's the secret behind the bending. Light moves a little slower through glass than through air. So when a ray hits the glass at an angle, one side slows down a hair before the other side does — and the whole ray pivots, like a marching band turning a corner because the inside row takes shorter steps.
