Please someone tell me why sun glasses have no power,though they are curved.......
They do very slightly distort light but because both surfaces are curved and parallel and the material thin the effect is minimal. Like looking through a window.
You can get prescription sunglasses, which do have 'power'.
A lens works because of a difference in curvature between the sides. A curved sheet of glass with parallel sides is neither concave nor convex and does not act as a lens. This statement only really applies for relatively thin glass that isn't 'very' curved. Extremely thick / curved glass sheets will distort images, although they don't behave like simple lenses either.
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