Scalar – a physical quantity that can be completely specified by its magnitude alone

Scattering – (of light) a process in which molecules of air have absorbed some light from a beam and then reradiated it in other directions

Schrödinger's equation – an equation, developed by Erwin Schrödinger in 1926, that treats the motion of particles with mass it terms of their wave characteristics (see equation 28.4)

Scientific notation – numerical short-hand which uses powers of ten as a simplified way of expressing numerical values (numbers are written with one digit to the left of the decimal times a power of ten)

Second law of thermodynamics – it is impossible for any system to undergo a cyclic process whose sole result is the absorption of heat from a single reservoir at a single temperature and the performance of an equivalent amount of work

Semiconductor – a crystal having a conductivity intermediate between those of an insulator and a metal (see table 31.1)

Shock wave– a single conical wave front formed when the speed of the sound source exceeds the speed of the wave

Short circuit– a circuit failure in which the current follows an alternative conducting path, usually parallel to the desired path, with lower resistance

Simple harmonic motion – motion which results when the acceleration is proportional to the negative of the displacement

Simple pendulum – a point (small) mass suspended by a light (of negligible mass) string

Simultaneous – occurring at the same time

Slope of a line – the ratio of the change in the line's ordinate (vertical value) to the corresponding change in the abscissa (horizontal value)

Solenoid– a helical winding of wire that, when carry a current, produces a uniform magnetic field near its center (see figure 19.30)

Space quantization – the only allowed values of orbital angular momentum for the electron are ones where the component along the direction of the field is an integer multiple of h/2p (see figure 28.21)

Spatial coherence – the phase difference between points on a wave front remains constant

Spatial frequency– the number of lines per unit length of the interference pattern; used to compute resolution requirements for film used in holography

Special theory of relativity – Developed and published in 1905 by Albert Einstein, it deals with the measurement of physical quantities by observers who are in uniform motion with respect to each other

Specific gravity – - the ratio of density of a material to the density of water at 4° Celsius

Specific heat – the energy required to change the temperature of a unit mass of a substance by 1° Celsius

Spectrometer– an instrument designed to analyze optical spectra (light )

Spectroscopy – the study of optical spectra (wavelengths)

Speed - the magnitude of instantaneous velocity

Spin – the angular momentum of an electron

Spontaneous emission – the emission of photons through the random de-excitation of excited atoms

Spring constant – the force necessary to stretch (or compress) a spring a unit length

Standing wave – a combination of waves that gives a stationary vibrational pattern (with nodes and antinodes)

State variables – quantities that describe the condition or state of a system, such as pressure, volume and temperature

Static equilibrium– that state of motion in which the velocity (of the center of mass) of a body is zero

Stoke’s law – describes the resistive force on an object as it moves through a fluid (see equation 10.11)

Streamline – a type of fluid flow in which each layer of fluid follows a smooth path past other layers without crossing over or becoming tangled (also called laminar flow)

Stimulated emission – process by which incident light of the proper frequency triggers emission of light (of the same frequency) by excited atoms

Subtractive primary colors – cyan, magenta, and yellow (see figure 30.22)

Surface tension– the ratio of the surface force to the length along which it acts

Symmetry – correspondence of opposite parts in size, shape, position, etc. An operation has symmetry if performing it leaves an object unchanged