| Glossary | ||||||||||||||
| coordinates
— individual values that collectively specify a position in one-, two-, or three-dimensional space. coulomb (C) — SI unit for electric charge. Coulomb’s law — attraction or repulsion between two charged objects is inversely related to the square of the distance between them and directly related to the magnitude of each of the charges. Also expressed as Fe = keq1q2/r2. crest — highest point or maximum amplitude of a wave. critical angle — angle of incidence at which light is totally reflected back into a material. cycle — something that repeats in time at regular intervals, such as one full swing of a pendulum. cyclotron radius — radius of circular (or helical) motion of a charged particle moving in a uniform magnetic field. Also called gyroradius. damping — gradual decrease in amplitude and energy of a wave due to friction or other energy-loss mechanisms. decibel (dB) — unit of power or amplitude that scales logarithmically, or by powers of 10. For example, an increase of 20 dB represents a factor of 10 increase in amplitude. An increase of 10 dB represents a factor of 10 increase in power, while an increase of 20 dB represents a factor of 100 increase in power. decimal places — number of digits in a numerical value that are to the right of the decimal point. density — ratio of mass to volume or the mass per unit volume. dependent variable — variable in an experiment that changes in response to changes made in the independent variable. The dependent variable is typically plotted as the vertical or y-axis (the ordinate) in a graph. destructive interference — occurs when two or more waves, which are out of phase with respect to each other, combine to create a smaller wave. | detector
— scientific instrument used to indicate the presence of radiation. diffraction — property of waves that describes how waves bend around obstacles and spread out when passing through openings. diffraction pattern — pattern of constructive and destructive interference, usually of light projected onto a screen, caused by diffraction around a barrier or through a narrow opening. diffuse reflection — light that strikes a surface that is rough (or not shiny) will scatter in many directions. Light striking the paint on a wall or the pages of a book are examples of diffuse reflection. digital multimeter — instrument with different settings that can measure current (ammeter), voltage (voltmeter), or resistance (ohmmeter). dispersion — separation of white light into its constituent colors (or wavelengths), such as by a prism or a rainbow. displacement — vector quantity that represents a change in position. Also used to describe the difference between an object’s initial and final positions. Measured in meters (m). Doppler effect — shift in frequency of a wave that is emitted from a source that is moving with respect to the observer. dose — total amount of radiation received by a person. Measured in rems. drag coefficient — dimensionless number that describes the effect of the shape of an object on fluid friction. An aerodynamic shape has a low drag coefficient and therefore lower air resistance compared to a shape with a higher drag coefficient. echo — reflected sound wave. efficiency — ratio of the output energy or power divided by the input energy or power for any process that transforms energy. (Note that input and output can be defined in different ways.) elastic collision — type of collision in which objects bounce off each other in a way that conserves total kinetic energy. (As in all collisions, momentum is also conserved for an elastic collision.) | |||||||||||||
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