# Chapter 29 & 30 conceptual physics

Reflection
The bouncing back of a particle or wave that strikes the boundary between two media
Normal
A line perpendicular to a surface
Angle of incidence
Angle between an incident ray and the normal to a surface
Angle of reflection
Angle between a reflected ray and the normal to a surface
Law of reflection
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
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
We will write a custom essay sample on
Any topic specifically for you
For only \$13.90/page
Diffuse reflection
the reflection of waves in many directions from a rough surface
Reverberation
Persistence of a sound, as in an echo, due to multiple reflections
Refraction
The change in direction of a wave as it crosses the boundary between two media in which the wave travels at different speeds.
Wave fronts
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
Mirage
A floating image that appears in the distance and is due to the refraction of light in Earth’s atmosphere
Dispersion
The separation of light into colors arranged according to their frequency, by interaction with a prism or diffraction grating, for example
Critical angle
The minimum angle of incidence for which a light ray is totally reflected within a medium
Total internal reflection
The 100% reflection (with no transmission) of light that strikes the boundary between two media at an angle greater than the critical angle
Optical Fiber
A transparent fiber, usually of glass or plastic, that can transmit light down its length by means of total internal reflection
Lens
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
Converging lens
A lens that is thickest in the middle, causing parallel 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. Also known as a 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 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.
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
Ray diagrams
A diagram showing 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. 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 from 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
small region in the center of our fie
ld of view in which out vision is most clear.