G482 KEY WORDS

Pregunta	Respuesta
Absorption Line Spectrum	A dark line of a unique wavelength seen in a continuous spectrum.
Ampere	The SI unit of electrical current
Amplitude	The maximum displacement of a particle from its equilibrium position.
Antinode	A point on a stationary wave with maximum amplitude.
Charge Carrier	Any charged particles, such as electrons, responsible for a current.
Coherent	Two sources are coherent when they emit waves with a constant phase difference.
Compression	A region in a sound wave where the air pressure is greater than its mean value.
Constructive Interference	When two waves reinforce to give increased amplitude.
Coulomb	The SI unit of electrical charge. A charge of 1C passes a point when a current of 1A flows for 1s. 1C=1A's
Destructive Interference	When two waves cancel to give a reduced amplitude.
Diffraction	The spreading of a wave when it passes through a gap or past the edge of an object.
Dispersion	The splitting of light into its different wavelengths.
Einstein Relation	This refers to the equation for the energy of a photon- that is: E=hf or E=
Electrical Resistance	The ratio of potential difference to current. Unit: ohm
Electrolyte	An electrically conducting solution. The conduction is due to positive and negative ions in the solution.
Electromagnetic Spectrum	A family of waves that travel through a vacuum at the speed of 3.0 x 10^8 ms-1
Electromotive Force (e.m.f.)	The energy gained per unit charge by charges passing through a supply. Unit: JC-1 or volt (V).
Electronvolt	The energy gained by an electron travelling through a p.d. of 1 volt. 1eV=1.6x10-19 J
Elementary Charge	The smallest unit of charge that a particle or an object can have. It has a magnitude of 1.6 x 10-19C
Emission Line Spectrum	A sharp and bright line of a unique wavelength seen in a spectrum.
Energy Level	The quantised energy states of an electron in an atom.
Frequency	The number of oscillations of a particle per unit time. Unit: Hertz (Hz)
Fundamental Frequency	The lowest frequency stationary wave for a particular system.
Ground State	The lowest energy state that can be occupied by an electron in an atom.
Intensity	The power transmitted normally through a surface per unit area: Intensity= power/cross sectional area. Unit: Wm-2
Interference	The formation of points of cancellation and reinforcement where two coherent waves pass through each other.
Internal Resistance	The resistance of an e.m.f. source. The internal resistance of a battery is due to its chemicals.
I-V characteristics	A graph of current against voltage for a particular component. You can identify a component from its I-V graph.
Kirchhoff's First Law	The sum of the currents entering any point (or junction) in a circuit is equal to the sum of the currents leaving that same point. This law conveys the conservation of charge.
Kirchhoff's Second Law	The sum of the e.m.f.'s round a loop in a circuit is equal to the sum of the p.d.'s in that same loop.
Light-emitting Diode (LED)	A semiconductor component that emits light when it conducts.
Longitudinal Wave	A wave in which particles oscillate along the direction in which the wave travels.
Lost Volts	The difference between the e.m.f. and the terminal p.d. It is also equal to the voltage across the internal resistance.
Magnetic Field	A force field created by magnets and moving charges.
Mean Drift Velocity	The average speed of charged particles along the length of a conductor.
Node	A point on a stationary wave with zero amplitude.
Number Density	The number of charged particles per unit volume. Unit: m-3
Ohm's Law	The current in a metallic conductor is directly proportional to the potential difference across its ends, provided its temperature remains constant.
Parallel	A term used when components are connected across each other in a circuit.
Path Difference	The difference in the distances travelled by two waves from coherent sources at a particular point.
Period	The time taken for one complete oscillation of a particle. Unit: Seconds (s)
Phase difference	The fraction of a cycle between the oscillations of two particles, expressed in degrees.
Photon	A quantum of electromagnetic energy.
Plane Polarised	Describes transverse waves that oscillate in only one plane.
Potential Difference (p.d.)	The energy lost per unit charge by charges passing through a component. Unit: JC-1 or volt (V).
Potential Divider	A circuit in which two or components are connected in series to a supply. The output voltage from the circuit is taken across one of the components.
Principle of Superposition	When two or more waves meet at a point, the resultant displacement is the sum of the displacements of the individual waves.
Progressive Wave	A wave that carries energy from one place to another.
Rarefaction	A region in a sound wave where the air pressure is less than its mean value.
Reflection	The bouncing back of a wave from a surface.
Refraction	The change in direction of a wave as it crosses an interface between two materials when its speed changes.
Resistivity	The property of a material defined by: resistivity=(resistance x cross-sectional area)/ Length Unit: Ohm meter
Resistor	An electrical component whose resistance in a circuit remains constant. Its resistance is independent of current or potential difference.
Resultant	Total or net
Semiconductor Diode	An electrical component made from a semiconductor material (e.g. silicon) that only conducts in one direction. A diode in 'reverse bias' has an infinite resistance.
Series	A term used when components are connected end-to-end in a circuit.
Stationary Wave	A wave pattern produced when two progressive waves of the same frequency travelling in opposite directions combine. It is characterised by nodes and antinodes. Also known as a standing wave.
Terminal p.d.	The potential difference across the external resistor connected to an e.m.f. source.
Threshold Frequency	The minimum frequency of the electromagnetic radiation that will eject electrons from the surface of a metal.
Transition	When an electron makes a 'jump' between two energy levels.
Transverse Wave	A wave in which the oscillation is at right angles to the direction in which the wave travels.
Wave	A periodic disturbance travelling through space, characterised by vibrating particles.
Wavelength	The distance between two adjacent peaks or troughs.
Work Function	The minimum energy required by a single electron to escape the metal surface.

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