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Chapter 30 Vocab.

Lens A piece of glass (or other transparent material) that can blend parrallel rays of light so that they cross, or appear to cross, at a single point.
Converging Lens A lens that is thickest in the middle, causing parrallel rays of light to converge to a focus. Also known as a convex lens.
Convex Lens A lens that is thickest in the middle, causing parallel rays of light to converge or focus. Also known as a converging lens.
Diverging Lens A lens that is thinnest in the middle and that causes parallel rays of light to diverge. Also known as a concave lens.
Concave Lens A lens that is thinnest in the middle and that causes parallel rays of light to diverge. Alos known as diverging lens.
Principal Axis The line joining the centers of curvature of the surfaces of a lens.
Focal Point For a converging lens, the point at which a beam of light parallel to the principal axis converges. For a diverging lens, the point from which such a beam appears to come.
Focal Plane A plane passing through focal point of a lens that is perpendicular to the principal axis.Converging lens,any incident parallel beam converges to a point somewhere on a focal plane.Diverging lens,such a beam comes from a point on a focal plane.
Focal Length The distance between the center of a lens and either focal point.
Real Image An image that is formed by converging light rays and that can be displayed on a screen.
Virtual Image An image formed through reflection or refraction that can be seen by an observer but cannot be projected on a screen because light from the object does not actually come to a focus.
Ray Diagram A diagram shpwing rays that can be drawn to determine the size and location of an image formed by a mirror or lens.
Eyepiece Lens of a telescope closest to the eye; enlarges the real image formed by the first lens.
Objective Lens In an optical device using compound lenses, the lens closest to the object observed.
Cornea The transparent covering over the eyeball.
Iris The colored part of the eye that surrounds the black opening through which light passes. The iris regulates the amount of light entering the eye.
Pupil The opening in the eyeball through which light passes.
Retina The layer of light-sensitive tissue at the back of the eye.
Farsighted Term applied to a person who has trouble focusing on nearby objects because the eyeball is so short that images form behind the retina.
Nearsighted Term applied to a person who can clearly see nearby objects but not clearly see distant objects. The eyeball is elongated so that images focus in front of rather than on the retina.
Astigmatism A defect of the eye caused when the cornea is curved more in one direction than in another.
Aberration Distortion in an image produced by a lens.
Fovea The middle of the retina, which is responsible for our central sharpest vision.
Blind Spot The small, circular, optically insensitive region in the retina where fibers of the optic nerve emerge from the eyeball.
Accommodation The process by which the eye increases the degree to which the lens converges or diverges light.
Created by: MLVeir