Physics Vocab.
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Created by:
supersam28 on May 29, 2010
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Description:
chapter 19-24
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Dunbar Study Stuff, NAQT, PC BEASTS, PCStudyGroup
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124 terms
Terms | Definitions |
|---|---|
 Harmonic motion | motion that repeats |
| Cycle | the unit of motion that repeats over and over (ex. A bicycle wheel, a full back-and-forth swing of a swing) |
| Oscillation | a motion that repeats regularly, usually indicating slow motion |
| Oscillator | a system with harmonic motion |
| Vibration | another word used for a motion that repeats regularly, usually indicating fast motion |
| Frequency | the number of cycles per second |
| Hertz | the unit of one cycle per second, which measures frequency |
| Period | the time for one cycle to occur |
| Amplitude | describes the 'size' of a cycle |
| Damping | the gradual loss of amplitude of an oscillator |
| Phase | tells you exactly where an oscillator is in its cycle; measured relative to the whole cycle, and is independent of amplitude or period; measured in degrees |
| Equilibrium | the central position; the system at rest, undisturbed, with zero net force |
| Restoring force | any force that always acts to pull the system back toward equilibrium |
| Natural frequency | the frequency or period at which a system naturally oscillates; every system has one |
| Resonance | occurs when a periodic force has the same frequency as the natural frequency of the system; 3 steps: periodic force, system, and response; occurs when: there is a system in harmonic motion like a swing, there is a periodic force like a push, the frequency of the periodic force matches the natural frequency of the system |
| Wave | an oscillation that travels from one place to another |
| Transverse | wave that has its oscillations perpendicular to the direction the wave moves |
| Longitudinal | wave that has vibrations in the same direction as the wave moves |
| Crest | the high point of the wave |
| Trough | the low point of the wave |
| Wavelength | the distance from any point on a wave to the same point on the next cycle of the wave; represented by Lambda (λ) |
| Standing wave | a wave that is confined in a space |
| Fundamental | the lowest natural frequency |
| Harmonics | natural frequencies found on a vibrating string; 'bumps' on the string |
| Nodes | points on a vibrating string where the string does not move |
| Antinodes | points on a vibrating string with the greatest amplitude |
| Propagate | spreading out from where something began |
| Plane wave | straight waves that move in a line perpendicular to the crest of the wave; caused by disturbing the line |
| Wave fronts | a pattern of parallel straight lines formed by the crests of a plane or circular waves |
| Circular wave | waves that move outward in a circle from the center; started by disturbing a single point, radiating outward from the center; create circular wave fronts |
| Reflection | the wave bounces and goes in a new direction |
| Refraction | the wave bends as it passes into and through an object |
| Diffraction | the wave bends around an object or through holes in the object |
| Absorption | the wave is absorbed and disappears |
| Boundaries | an edge or surface where things change suddenly; where conditions or materials change, affecting the wave |
| Superposition Principle | states that the total vibration at any point is the sum of the vibrations from each individual wave |
| Interference | happens when two or more waves mix together |
| Wave pulse | a short length of wave, maybe just a single oscillation |
| Constructive interference | occurs when waves add up to make a larger amplitude; useful in working with light and sound |
| Destructive interference | occurs when waves add up to make a wave with smaller or zero amplitude |
| Pitch | how you hear and interpret a sound's frequency |
| Decibels | the measurement of loudness of sound |
| Acoustics | the science and technology of sound |
| Subsonic | objects that move slower than sound |
| Supersonic | objects that move faster than sound |
| Shock wave | a cone shaped wave that forms where the wave fronts pile up; in front of the wave there is total silence, behind the wave you can hear the noise from the plane, right at the wave the amplitude changes abruptly, causing a sonic boom |
| Doppler effect | occurs when a sound source is moving at speeds below the speed of sound, when an observer hears the frequency at which wave fronts arrive at his or her hears |
| Reverberation | a multiple echo caused by the reflected sound and direct sound together; can make good and bad sounds depending on the effect |
| Fourier's theorem | states that a wave of any shape can be made by adding up single frequency waves |
| Frequency spectrum | a graph showing the different frequencies present in a sound; vertical axis tells you the loudness and the horizontal axis tells you the frequency |
| Sonogram | shows how loud sound is at different frequencies over a period of time |
| Cochlea | a tiny fluid-filled organ in the inner ear where we get our sense of hearing |
| Rhythm | a regular time pattern in a sound |
| Musical scale | a pattern of frequencies that creates most of music |
| Note | each frequency in a musical scale |
| Octave | the range between any frequency and twice that frequency |
| Harmony | the study of how sounds work together to create effects desired by the composer |
| Beat | the sound when two frequencies of sound are close but not exactly equal; useful for determining if an instrument is out of tune |
| Consonance | the sound of more than one frequency of sound and the combination sounds good |
| Dissonance | the sound of more than one frequency of sound and the combination sounds bad |
| Incandescence | the process of making light with heat |
| Fluorescence | the process of atoms releasing electrical energy as light |
| Intensity | the amount of light energy per second falling on a surface |
| White light | light without any color; the combination of all the colors |
| Photoreceptors | light-sensitive cells on the surface of the retina; when light hits it, the cell releases a chemical signal that travels along the optic nerve to the brain, where the signal is translated into a perception of color; signal that is sent depends on how much energy the light has |
| Cones | photoreceptors that respond to color; three types that respond best to red, green, and blue |
| Rods | photoreceptor that responds only to differences in intensity; detect black, white, and shades of gray; more sensitive than other cone cells especially in low light levels |
| Additive color process | where three photoreceptors (red, green, blue) in the eye operate together so that we see millions of different colors; the color seen depends on how much energy is received by each of the 3 cone cells |
| Additive primary colors | red, green, blue |
| Subtractive color process | process where chemicals known as pigments in the dyes and paints absorb some colors and reflect other colors; used in colored fabrics, paints, etc. |
| Pigments | chemicals in dyes that work by taking away colors from white light, absorbing some colors and reflecting other colors |
| Subtractive primary colors | cyan, magenta, yellow; when added make black, which is the absence of color |
| CMYK color process | another name for the subtractive color process, made up of the colors cyan, magenta, yellow, and black; used for making all colors that are seen in reflected light, including printing inks and fabric dyes; the three pigments are combined in various proportions to make any color, all together making black |
| RGB color process | an additive process that used red, green and blue light; used by television screens and computer monitors |
| Optics | the study of how light behaves |
| Light ray | an imaginary line that represents a thin beam of light |
| Converging lens (convex lens) | lens that bends light so that the light rays come together to a point |
| Diverging lens (concave lens) | lens that bends light so it spreads light apart instead of coming together; items appear smaller |
| Prism | an optical device made of a solid piece of glass with flat polished surfaces; can both bend and/or reflect light; used in telescopes, cameras, and supermarket laser scanners; ex.) diamond |
| Translucent | if some light can pass through an object but the light is scattered in many directions (Ex. Tissue paper, frosted glass) |
| Transparent | materials that allow light to pass through (ex. Glass, plastic, air) |
| Specular reflection | where each ray of light bounces off in a single direction; created on polished surfaces, where you see the reflections of other things but not the surface itself |
| Diffuse reflection | where a single ray of light scatters into many directions due to a surface that is not shiny; caused by the roughness of a surface, even on microscopic level; when looked at, you see the surface itself |
| Incident ray | the light ray that strikes the object |
| Reflected ray | the light ray that bounces off the object |
| Normal line | an imaginary line between the incident and reflected rays, that is perpendicular ot the surface of the object |
| Angle of incidence | the angle between the incident ray and the normal line |
| Angle of reflection | the angle between the normal line and the reflected ray |
| Ray diagram | an accurately drawn sketch showing how light rays interact with mirrors, lenses, and other optical devices |
| Index of refraction (n) | measures the ability of the material to bend light |
| Angle of refraction | the angle between the refracted ray and the normal line |
| High index to low index | bends away from normal line |
| Low index to high index | bends toward normal line |
| Total internal reflection | the effect when the angle of incidence increases, there is a point at which the light will not enter the air but reflect back into the object; occurs when the angle of incidence is greater than the critical angle for a material |
| Critical angle | the angle of incidence at which the angle of refraction is 90 degrees; depends on the index of refraction of the material; at angles of incidence greater than this angle for a material, total internal reflection occurs |
| Fiber optics | thin glass fibers that use total internal reflection to carry light, even around bends and corners; this technology is important to the communications industry |
| Dispersion | describes how refractive index varies depending on the color of light |
| Objects | real physical things that give off or reflect light rays |
| Images | 'pictures' of objects that are formed in space where light rays meet; formed by our eyes, mirrors, lenses, prisms, and other optical devices |
| Virtual image | the image in a mirror, where the light rays do not actually come together to form the image, they only appear to come together; the illusion is created by our eyes and brain |
| Optical axis | the imaginary line that goes through the center of the lens; light traveling along this line is not bent at all by the lens |
| Focal point | a point where light rays that enter a converging lens parallel to its axis bend to meet; there will always be two, on either side of the lens |
| Focal length | the distance from the center of the lens ot the focal point; usually the same for both focal points of a lens |
| Real image | light from each single point on an object comes back together again at a single point in another place to make an image, formed by a converging lens |
| Focus | the place where the light comes together again; where you see the image clearly |
| Magnification | the ratio of the size of the image divided by the size of the object; makes images smaller, larger or equal to life size |
| Refracting telescope | has two converging lenses with different focal lengths; used by microscopes and telescopes to get a higher magnification |
| Electromagnetic wave | waves produced by oscillations of electricity or magnetism |
| Electromagnetic spectrum | the entire range of electromagnetic waves, including all possible frequencies |
| Radio waves | the lowest-frequency waves; wavelengths: kilometers to tens of centimeters; need to be high to efficiently create the large wavelengths they use; (ex. Broadcast towers) |
| Microwaves | range from 30 cm to about 1 mm; often are tuned to the natural frequency of liquid water molecules (ex. Microwaves, cell phones) |
| Infrared light | wavelength: from 1mm to 700nm; often referred to as radiant heat; although we cannot see them, we can feel them with our skin (ex. Infrared waves, heat from the sun) |
| Visible light | wavelength: 700 to 400 nm; includes all the colors of light we see when white light is split by a prism; the term 'light' commonly refers to this part of the spectrum; comes from the sun |
| Ultraviolet light | wavelength: 10 to 400 nm; has enough energy to remove electrons and break chemical bonds (ex. Sunlight, can be beneficial and dangerous to humans; most blocked by ozone layer) |
| X-rays | high-frequency waves used extensively in medical and manufacturing applications; wavelength: 10 nm to .001 nm (ex. X-rays) |
| Gamma rays | generated in nuclear reactions; can push even the inner electrons right out of an atom and completely disrupt chemical bonds; wavelength: less than about ten-trillions of a meter; very dangerous without a heavy shield |
| Double Slit experiment (Thomas young) | famous experiment that gave strong evidence that proved that light is a wave due to an interference pattern can lonely be created by the addition of waves; showed that two beams of light could interfere with each other by letting light pass through tow very thin slits, where light fell on the screen |
| Diffraction grating | creates an interference pattern similar to the pattern for the double slit; a series of thin parallel grooves on a piece of glass or plastic; when light goes through, each groove scatters the light so the grating acts like many parallel slits |
| Central spot | a bright spot that appears directly in front of a diffraction grating where the light passes straight through |
| Diffraction pattern | a series of bright spots on either side of the central bright spot; closest bright spots are called first order |
| Polarizer | a material that allows light of only one polarization to pass through; light that comes through has only one polarization making it polarized light |
| Polarization | the orientation of light, either horizontal or vertical (based on the direction of the oscillation of the wave perpendicular to the direction the wave moves |
| Photons | little bundles of divided light waves; described as 'particle-like'; each atom that makes light gives; absorbs only one at a time |
| Photoluminescence | the process of releasing stored light energy |
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