Chapter 29 & 30 conceptual physics
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Reflection
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The bouncing back of a particle or wave that strikes the boundary between two media
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Normal
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A line perpendicular to a surface
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Angle of incidence
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Angle between an incident ray and the normal to a surface
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Angle of reflection
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Angle between a reflected ray and the normal to a surface
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Law of reflection
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The angle of incidence for a wave that strikes a surface is equal to the angle of reflection. This is true for both partially and totally reflected waves
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Virtual image
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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
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Diffuse reflection
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the reflection of waves in many directions from a rough surface
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Reverberation
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Persistence of a sound, as in an echo, due to multiple reflections
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Refraction
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The change in direction of a wave as it crosses the boundary between two media in which the wave travels at different speeds.
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Wave fronts
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The crest, trough, or any continuous portion of a two-dimensional or three-dimensional wave in which the vibrations are all the same way at the same time
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Mirage
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A floating image that appears in the distance and is due to the refraction of light in Earth's atmosphere
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Dispersion
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The separation of light into colors arranged according to their frequency, by interaction with a prism or diffraction grating, for example
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Critical angle
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The minimum angle of incidence for which a light ray is totally reflected within a medium
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Total internal reflection
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The 100% reflection (with no transmission) of light that strikes the boundary between two media at an angle greater than the critical angle
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Optical Fiber
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A transparent fiber, usually of glass or plastic, that can transmit light down its length by means of total internal reflection
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Lens
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A piece of glass (or other transparent material) that can bend parallel rays of light so that they cross, or appear to cross, at a single point
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Converging lens
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A lens that is thickest in the middle, causing parallel rays of light to converge to a focus. Also known as a convex lens
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Convex lens
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A lens that is thickest in the middle, causing parallel rays of light to converge or focus. Also known as a converging lens.
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Diverging lens
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A lens that is thinnest in the middle and that causes parallel rays of light to diverge. Also known as a concave lens
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Concave lens
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A lens that is thinnest in the middle and that causes parallel rays of light to diverge. Also known as a diverging lens
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Principal axis
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The line joining the centers of curvature of the surfaces of a lens
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Focal point
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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.
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Focal plane
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A plane passing through either focal point of a lens that is perpendicular to the principal axis. For a converging lens, any incident parallel beam of light converges to a point somewhere on a focal plane. For a diverging lens, such a beam appears to come from a point on a focal plane.
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Focal length
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The distance between the center of a lens and either focal point
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real image
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An image that is formed by converging light rays and that can be displayed on a screen
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Ray diagrams
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A diagram showing rays that can be drawn to determine the size and location of an image formed by a mirror or lens
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Eyepiece
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Lens of a telescope closest to the eye; enlarges the real image formed by the first lens
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Objective lens
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In an optical device using compound lenses, the lens closest to the object observed
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Cornea
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The transparent covering over the eyeball
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Iris
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The colored part of the eye that surrounds the black opening through which light passes. Regulates the amount of light entering the eye
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Pupil
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The opening in the eyeball through which light passes
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Retina
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The layer of light-sensitive tissue at the back of the eye
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farsighted
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Term applied to a person who has trouble focusing on nearby objects because the eyeball is so short that images from behind the retina
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Nearsighted
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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
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Astigmatism
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A defect of the eye caused when the cornea is curved more in one direction than in another
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Aberration
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Distortion in an image produced by a lens
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fovea
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small region in the center of our fie ld of view in which out vision is most clear.
