Business / Machine Shop / Concave: A curved depression in the surface of an object.
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Entertainment / Photography / Concave Lens: See bi-concave lens. MORE
Entertainment / Photography / Bi-Concave Lens: Simple lens or lens shape within a compound lens, whose surfaces curve toward the optical center. Such a lens causes light rays to diverge. MORE
Entertainment / Photography / Reflecting Telescope: Telescope using a concave parabolic mirror to increase focal length and focus light at a point. MORE
Business / Machine Shop / Radius Gage: Any one of a number of small, flat, standard-shaped metal leafs or blades used for checking the accuracy of regular concave and convex surfaces. MORE
Entertainment / Photography / Negative Lens: Is a simple concave lens that causes rays of light to diverge away from the optical axis. MORE
Entertainment / Photography / Meniscus Lens: Is a simple lens consisting of a single piece off glass, thicker at the center than at the edges. It has one concave and one convex face. MORE