| A | B |
|---|
| ray diagram | a diagram that shows how light rays change in direction when they strike mirrors and pass through lenses |
| angle of incidence | the angle an incident ray makes with a line perpendicular to a surface it strikes |
| angle of reflection | the angle reflected ray makes with a line perpendicular to a surface it strikes |
| plane mirror | a mirror with a flat surface |
| virtual image | a copy of an object formed at the point from which light appears to be comming |
| concave mirror | a mirror that is curved inward |
| focal point | the point at which light rays parallel to the axis of a mirror or lens meet or appear to meet |
| real image | a copy of an object formed at the point where light rays actually meet |
| covex mirror | a mirror that is curved outward |
| index of refraction | the ratio of the speed of lightin a vacum to the speed of light in a medium |
| lens | an object made of any thin, transport material that has one or two curved surfaces that can refract light |
| concave lens | a lens that is curved inward at the center and its thickest at the outside edges |
| convex lens | a lens that is curved outward at the center and is thinnest at the outside edge |
| critical angle | the angle of incidence that produces an angle of refraction equal to 90 degrees |
| total internal reflection | the complete reflection of a light ray back into its original medium when the angle of incidenceis greater than the critical angle of refraction |
| telescope | an optical instrument that uses lenses and/or mirrors to collect and focus light from distant object |
| reflecting telescope | a telescope that uses mirrors and convex lenses to collect and focus light |
| refracting telescope | a telescope that uses only lenses to collect and focus light |
| camera | an optical intrument that records an image of an object |
| microscope | an optical instrument that uses lenses to provide enlarged images of very small, near objects |
| cornea | the transparent outer coating of the eye |
| pupil | the opening that allows light to enter the eye |
| iris | the colored part at the front of the eye, which expands and contracts to control the amount of light entering the eye |
| retina | the inner surface of the back of the eye, containing light-sensitive nerve endings |
| rods | light-sensitiveneurons in the retina that detect low-intesity light and distinguish black, white, and gray |
| cones | light-sensitive neurons in the retina that detect color |
| nearsightedness | an eye condition in which distant objects are blurry |
| farsightedness | an eye condition that cause nearby object to be blurry |
| astigmatism | an eye condition in which objects at any distance appear blurry because of the distorted shape of the cornea |
