| Concave | Convex
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| Concave means curved like a segment of the interior of a circle or hollow sphere; hollow and curved. | Convex means having a surface that is curved or rounded outward.
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The arrow is pointing to the concave surface.
The surface curves inward. |  |
|  | The arrow is pointing to the convex surface.
The surface bulges outward. |
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The arrow is pointing to the concave surface.
The surface curves inward. |  |
|  | The arrow is pointing to the convex surface.
The surface bulges outward. |
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| Double concave lens (is a diverging lens). |  |
|  | Double convex lens (is a converging lens). |
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| Concave mirror. |  |
|  | Convex mirror. |
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