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# IB SL Physics Terms

### ALL UNITS

Term | Definition |
---|---|

accurate | average value moves towards true value |

precise | data are close together |

random error | positive and negative values around average value / values are scattered or have wide range |

systematic error | error is identical for each reading; error deviates from the correct value by the same fixed amount |

coefficient of friction | ratio between maximum friction and normal reaction |

elastic collision | collision in which kinetic energy and momentum are conserved |

force | net force is rate of change of momentum |

impuse | change in momentum |

momentum | product of mass and velocity |

first law | a body continues at rest or constant velocity unless acted on by a resultant external force |

second law | rate of change of momentum of a body is equal to/directly proportional to force acting on body |

third law | when two bodies A and B interact, the force that A exerts on B is equal and opposite to the force that B exerts on A - force on Body A is equal in magnitude to force on Body B (from A) - forces are in opposite directions - forces are of same kind |

translational equilibrium | sum of net forces action on object is zero |

work | distance moved in direction of force energy transferred from one location to another |

centre of gravity | point where weight/gravitational force of object appears to act |

boyle's law | for an ideal gas at constatnt temeprature, pressure is inversely proportional to volume |

thermal capacity of body | energy required to increase temeprature of a substance by 1 degree celsius or q kelvin |

ideal gas | gas that obeys universal gas law at all pressures, volumes, and temperatures; gas in which there are no IMFs; molecules have zero potential energy, only kinetic energy |

internal energy | sum of kinetic energy and intermolecular potential energy |

specific heat capacity | thermal energy/heat required to change the temperature of a substance by 1 kelvin/1 degree celsius per unit mass |

latent heat of fusion | thermal energy absorbed/released when a unit mass of liquid freezes to become solid at CONSTANT TEMPERATURE; or solid melts to become liquid at CONSTANT TEMPERATURE |

latent heat of vaporization | quantity of thermal energy/heat required to convert unit mass of liquid to vapour with CONSTANT TEMPERATURE/at BOILING POINT |

temperature of substance | temperature is proportional to measure of average kinetic energy of molecules/particles of substance |

thermal capacity | thermal energy required to raise temperature of object by 1 kelvin or 1 degree celsius |

thermal energy | non-mechanical transfer of energy between two different bodies as a result of a temperature difference between them |

thermal equilibrium | rate of energy absorption is equal to the rate of energy emission |

amplitude | maximum displacement of system from equilibrium/centre of motion |

coherent | constant/zero phase difference between light waves |

constructive interference | when two waves meet; resultant displacement found by summing individual displacements; displacement greater than that of individual wave/to give max displacement |

continuous travelling wave | energy transfer; no interruption in transfer/without mass motion of medium |

critical angle | when transmitted ray/light in medium 2 is along boundary/REFRACTED AT 90 degrees; angle of incidence in medium 1 is critical angle OR when ray/light is incident on boundary at angle greater than critical angle of medium; ray is not transmitted --> TIR |

diffraction | when a wave front passes by/incident on edge/slit; wave bends/spreads into geometrical shadow - spreading out of a wave when it meets an aperture/gap/slit/obstancle |

displacement (with reference to waves) | distance in a particular direction from its mean position |

electromagnetic wave | oscillating/vibrating electric and magnetic fields at right angles to each other; at right angles to direction of propagation/energy transfer of wave/velocity/transverse can travel through vacuum |

frequency of source | number of oscillations/vibrations per unit time |

interference | when waves overlap, resultant displacement is sum of individual displacements |

intensity of sound wave | power per unit area |

longitudinal wave | wave where displacement of particles/oscillations of particles is parallel to direction of energy propagation |

monochromatic | single/same wavelength/frequency |

node | zero displacement |

principle of superposition | when 2 waves meet/interfere --> resultant displacement of medium/particles is vector sum of their individual displacements |

polarized light | light in which the electric/magnetic field (vector) vibrates only in one plane/electric field oscillates/vibrates in one plane only |

ray | direction which energy of wave travels |

resonance | maximum amplitude of oscillation, when a periodic force is applied to it, and the frequency of the force is equal to the natural frequency of vibration of the system |

refractive index | ratio of speed of light in vacuum to speed of light in a substance |

SHM | force/acceleration are proportional to the displacement/distance from a mean position; directed towards this equilibrium point, in opposite direction of displacement/distance |

transverse wave | direction of energy propagation is at right angles to vibration of particles in medium |

travelling wave | wave that transfers energy between points in a medium |

TIR | for a ray attempting to move from high to low refractive index medium; phenomena in which angle of incidence is greater than critical angle; critical angle is angle of incidence for which angle of refraction is 90 degrees; leading to a REFLECTED ray |

unpolarized light | all possible polarization directions are equall represented/ direction fo polarization is random |

wavefront | line that joins points with same phase, of same crest trough |

wavelength | distance moved by wave during one oscillation of the source; |

wave speed | • distance travelled per unit time; • by the energy of the wave / by a wavefront; OR rate at which energy is propagated along wave |

coulomb's law | • the force between two (point) charges; • is inversely proportional to the square of their separation and (directly) proportional to (the product of) their magnitudes; |

electric current | The amount of charge that flows through a cross-sectional area of a conductor per unit time. OR Rate of flow of chart through a conductor; |

electric field strength | • electric force per unit charge • acting on a small/test positive charge |

electric field | • region/area/volume (of space); • where a charge experiences a force; |

electric p.d. | • Work done/energy per unit charge; (ratio idea necessary) • to move positive test charge between points (in an electric field); Work done per unit charge |

electric resistance | potential difference across the wire/component divided by the current through the wire/component |

emf | the work done per unit charge in moving a quantity of charge completely around a circuit --> ⭐ OR power delivered by the supply per unit current |

ideal voltmeter | infinite resistance OR draws no current from circuit/component OR has no effect on the circuit |

internal resistance of cell | • resistance of the components/chemicals/materials within the cell itself {not “resistance of cell”}; • leading to energy/power loss/dissipated in driving current through the cell; |

kirchoff's first law | ΣI = 0 at junction |

kirchoff's second law | Σemf = Σp.d. around a loop/circuit |

ohm's law | potential difference proportional to current, provided that the temperature/physical conditions are constant V = IR |

gravitational field | • region/area/volume (of space); • where a mass experiences a force; |

gravitational field strength | • the «gravitational» force per unit mass; • exerted/acting on a point/small/test mass; |

gravitational field strength at a point | • force per unit mass • acting on a small/test/point mass «placed at the point in the field» |

newton's universal law of gravitation | • the (attractive) force between two point masses; • is directly proportional to the product of the masses; • and inversely proportional to the square of the distance (between their centres of mass); |