Page 561 - Physics Coursebook 2015 (A level)

Glossary
free oscillation An oscillation at is the natural frequency of the oscillator.
frequency The number of oscillations per unit time. Unit: hertz (Hz).
frequency modulation A form of modulation in which the signal causes variations in the frequency of a carrier wave.
fundamentalfrequency Thelowest-frequencystationary wave for a particular system.
gain The voltage gain of an amplifier is the ratio of the output voltage to the input voltage.
geostationary orbit The orbit of an artificial satellite which has a period equal to one day so that the satellite remains above the same point on the Earth’s equator. From Earth the satellite appears to be stationary.
gravitational field A region where any object with mass experiences a force.
gravitational field strength The gravitational force experienced by an object per unit mass:
g = mF
gravitational potential The gravitational potential energy
per unit mass at a point in a gravitational field.
gravitational potential energy The energy a body has due to its position in a gravitational field.
ground state The lowest energy state that can be occupied by an electron in an atom.
hadron Any particle which is affected by the strong nuclear force, made from two or three quarks or anti-quarks.
half-life The mean time taken for half the number of active nuclei in a radioactive sample to decay.
half-thickness The mean thickness of an absorbing material required to reduce the intensity of radiation by half.
Hall effect The production of a voltage across a conductor when a current flows through the conductor at right angles to a magnetic field.
Hall voltage The voltage produced across a conductor when a current flows through the conductor at right angles to a magnetic field; used in a Hall probe to measure B since VH ∝ B.
harmonic A wave of frequency n times the fundamental frequency, where n is an integer.
Hooke’s law The extension produced in an object is proportional to the force producing it.
ideal gas A gas that behaves according to the equation pV=nRT or pV=NkT.
ideal gas equation for an ideal gas: pV=nRT or pV=NkT
(Also known as the ideal gas equation.)
image intensifier A device used to change a low-intensity X-ray image into a bright visual image.
impedance matching The reduction in intensity of ultrasound reflected at the boundary between two substances, achieved when the two substances have similar acoustic impedances.
independent variable The variable in an experiment with a value that is altered by the experimenter.
inelastic A collision is inelastic when kinetic energy is not conserved; some is transferred to other forms such as heat. Momentum and total energy are always conserved.
inertia A measure of the mass of an object. A massive object has large inertia.
instantaneous speed The speed of an object measured over a very short period of time.
intensity The power transmitted normally through a surface per unit area: power
intensity = cross-sectional area Unit: Wm−2.
interference The formation of points of cancellation and reinforcement where two coherent waves pass through each other.
internal energy The sum of the random distribution of kinetic and potential energies of the atoms or molecules in a system.
internal resistance The resistance of an e.m.f. source. The internal resistance of a battery is due to the chemicals within it.
intrinsic semiconductor A pure substance whose resistivity is intermediate between that of a conductor and an insulator.
inverting amplifier A circuit, involving the use of an amplifier, where the output is 180° out of phase with the input.
ion An atom with a net positive or negative charge. isotopes Nuclei of the same element with a different
number of neutrons but the same number of protons.
I–V characteristic A graph of current against voltage for a particular component of an electrical circuit.
kinematics The study of motion using quantities such as time, distance, displacement, speed, velocity and acceleration.
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