Download G482 Definition List

G482 - Electrons, Waves and Photons
Definition List
COULOMB
The charge transported by a steady current of one ampere in one second
ELECTRIC CURRENT
CONVENTIONAL
The flow of charged particles
Direction in which positive charges would flow in a circuit
CURRENT
RESISTANCE
Potential Difference / Current
RESISTIVITY
Resistivity = R A / L, where R is the resistance of the material, A is the
cross-sectional area of the material and L is the length of the material
OHM's LAW
For a metallic conductor at constant temperature, the current in the
conductor is directly proportional to the potential difference across
its ends.
KIRCHHOFF'S
The sum of the currents entering a point is equal to the sum of the
FIRST LAW
currents leaving the same point
KIRCHHOFF'S
The sum of the e.m.f.'s around any closed loop in a circuit is equal
SECOND LAW
to the sum of the p.d.'s around the same closed loop
MEAN DRIFT
The average distance travelled by the electrons along the wire per
VELOCITY
second
KILOWATT-HOUR
The energy transformed by a 1 kW device in a time of 1 hour
POTENTIAL
The energy transferred (lost) per unit charge
DIFFERENCE
ELECTROMOTIVE
The energy transferred (gained) per unit charge
FORCE
PROGRESSIVE
A transfer of energy as a result of the oscillations of the
WAVE
medium or particles through which the energy is travelling
LONGITUDINAL
Wave vibrations are parallel to the wave direction
WAVE
TRANSVERSE
Wave vibrations are perpendicular to the wave direction
WAVE
DISPLACEMENT
The distance of a point on the wave from the equilibrium
(WAVES)
position
AMPLITUDE
The maximum displacement of any point on the wave from the
(WAVES)
equilibrium position
WAVELENGTH
The distance from any point on the wave to the next
(WAVES)
subsequent point in phase
WAVE SPEED
The speed at which energy is transmitted by the wave
(WAVES)
FREQUENCY
The number of oscillations at a point per unit time
(WAVES)
PERIOD
The time taken for one complete oscillation
(WAVES)
INFRARED RADIATION
Part of the EM spectrum with a wavelength of 1 x 10-6 m
INTERFERENCE
When two waves meet at a point, there is a change in the overall
displacement
PRINCIPLE OF
When two waves interfere at a point, the resultant displacement
SUPERPOSITION
is the sum of the individual displacements
PATH
The extra distance travelled by one of the waves compared with the
DIFFERENCE
other
COHERENCE
A constant phase difference between the waves
COHERENT
Sources of waves which have a constant phase difference
SOURCES
DIFFRACTION
The spreading out of a wave after passing through a gap or around
an obstacle
PLANE
Plane polarised waves oscillate in one plane only
POLARISATION
INTENSITY
The rate of energy transmitted per unit area at right angles to the
direction of propagation (W/m2)
STANDING
A wave consisting of nodes and antinodes which does not transfer energy
WAVE
NODE
A point where the amplitude of vibrations is always zero
ANTINODE
A point where the amplitude of vibrations takes the maximum
possible value
THRESHOLD
The minimum frequency of radiation needed for electrons to be
FREQUENCY
ejected from a metal surface
PHOTON
A packet of energy OR a quantum of electromagnetic radiation
ELECTRONVOLT
The energy gained by an electron which is accelerated through
a potential difference of 1 volt
WORKFUNCTION
The minimum energy required to eject an electron from a metal
OF A METAL
surface
CONTINUOUS
All wavelengths are present in the radiation
SPECTRUM