Question

explain why the sun glasses have no power

Answer 1

it's false sun galsses too have a small power in it because a powerless glass means the focal point should be at infinity.

Answer 2

Hi there!

Eyeglass are a complicated shape, because the eye moves around slightly as you look in different directions.

But, a lens that has both surfaces at the same angle to the light as it passes through the surface first bends the light one way, then back, through exactly the same angle; it may move the ray sideways but it does not change it's direction. That's what zero power means.

So a good quality zero power sunglasses lens have both front and back surfaces quite strangely shaped, but they conspire to not change the apparent distance of what you see through them.

Hope it helps u!!