# Definitions from Past Papers (Physics)

All the definition questions from OCR Unit 2 AS Physics from June 2009 to June 2012. Answers taken from the mark schemes.

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Sarah Stancombe- Electrons, Waves and Photons (G482)
Definitions
June 2009
Resistance- resistance = p.d./current
Kirchhoff's second law- (sum of) e.m.f.s = sum /total of p.d.s/sum of voltages (in a loop).
January 2010
Mean Drift Velocity- the average displacement/distance travelled of the electrons along the wire per
second. (Over time) they move slowly in one direction through the metal lattice (when there is a p.d. across
the wire) (because) they collide constantly.
Resistivity- resistance time the cross-sectional area, divided by the length (= RA/l).
Wavelength- distance between (neighbouring) identical points/points with same phase (on the wave).
Frequency- number of waves passing a point /cycles/vibrations (at a point) per unit time/second.
Speed (of a wave)- distance travelled by the wave (energy) per unit time/second.
Infra-red Radiation- infra red is part of the e-m spectrum longer than the visible light (10-5 7.5x10-7).
Interference- when (two) waves interact (at a point) there is a change in overall displacement.
Coherence- constant phase difference/relationship (between the waves).
Diffraction- paths spread out after passing through a gap or around an obstacle.
June 2010
Kilowatt-hour- (a unit of) energy equal to 3.6 MJ.
Intensity- intensity is the (incident) energy per unit area per second.
Line Spectrum- light emitted from (excited isolated) atoms produces a line spectrum a series of
(sharp/bright/coloured) lines against a dark background.
January 2011
Electronvolt- an eV is the energy acquired by an electron accelerated/moves through a p.d. of 1 V (1 eV = 1.6
x 10-19J ).
de Broglie Wavelength- Electrons are observed to behave as waves/show wavelike properties where the
electron wavelength depends on its speed/momentum.
Photon- a particle of (e-m) energy/light.
Continuous Spectrum- all wavelengths/frequencies are present (in the radiation).
June 2011
Potential Difference- energy transfer per unit charge from electrical to other forms.
Intensity- energy per unit area per unit time.

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Sarah Stancombe- Electrons, Waves and Photons (G482)
Work Function- the minimum energy (required) to release an electron (from the surface of the metal).
Plane Polarised Wave- a transverse wave in the plane normal to the direction of (energy) propagation.
Oscillations confined to a single plane (containing the direction of propagation).
January 2012
e.m.f- energy transferred from source/changed from some form to electrical energy per unit charge.…read more