IB Physics Vocabulary

247 terms by amycompare 

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absolute uncertainty

a direct statement of the confidence limits of a reading

absolute zero

the extrapolated temperature at which the pressure and volume of an ideal gas are predicted to be zero; the temperature at which the molecules have no random kinetic energy.

absorption spectra

When a continuous spectrum of light is shone through and element in gaseous form, specific frequencies are preferentially absorbed. the resulting spectrum (with some frequencies missing) is know as the element's ...

acceleration

the rate of change of velocity in a particular direction; a vector quantity

accuracy

the measured value is close to the true value; small systematic error

activity

the rate of decay of a radioactive source; the number of nuclei tht decay per unit time

adiabatic

A _____ change is one that takes place without any energy transfer to or from the gas.

albedo

Some of the radiation received by a planet is relected back into space. The _____ of a sruface is the fration of the power that is scattered (reflected) from the surface compared to total incident power received. It's a ratio and has no units.

alpha particles

helium nuclei (two protons and two neutrons) emitted as a result of a decaying unstable nucleus.

amplitude

the maximum displacement from the mean (during one oscillation)

analogue

encodes the information using a range of possible values

analyser

a polerizer used to dectect polarized light

angular frequency

used in SHM; 2pi divided by the period

angular velocity

when an object is undergoing uniform circular motion at constant speed, _____ is the rate of change of angle (as measured between the radius from the center of the circle to the object and one of the axis).

antinodes

a point on a standing wave that has the maximum amplitude

artificial (induced ) transmutation

can take place when a nucleus is bombarded by a nucleon, and alpha particle, or other small nucleus. The target nucleus first captures the incoming object and then an emission or decay takes place.

Avogadro constant

the number of atoms in 0.012 kg of carbon-12; one mole

average (speed, velocity, acceleration)

the steady (constant) value that would have given the same result

Bainbridge mass spectrometer

_____ allows the isotopic content of a sample to be measured. ions of the same velocity but different mass will follow different circular pathts when moving in a constant perpendicular magnetic field.

beta - decay

the emission of a fast-moving electron when a neutron decays into a proton, beta particle (negative), and an anitneutrino

beta + decay

the emission of a fast-moving positive electron (positron) when a proton decays into a neutron, a beta (positive) particle, and a neutrino

beta particles

fast moving electrons or positrons that have been emitted as a result of a decaying unstable nucleus

binary numbers

numbers to the base of 2; the only possible digits are 1 or 0

binding energy

the amount of energy that is released when a nucleus is assmebled form its component nucleons. It's also the amount of energy that needs to be added in order to separated in nucleus into its individual nuleons.

binding energy per nucleon

the total binding energy for a particular nucleus divided by the number of nucleons contained in the nucleus; _____ represents a nucleus that is more energetically stable.

bit

a single binary digit, which will be either 1 or 0

black-body radiation

At a given temperature, different surfaces will radiate different amounts of EM radiation. The maximum theoretical amount that can be emitted from any surface is known as _____.

boiling

the process by which molecules of a liquid spontaneous change from the liquid phase into the gas phase throughout the body of the liquid

Brewster's law

At one particular angle of incidence, EM will be completely polarized

Capacitance

the charge divided by the potential difference

carbon dioxide storage and capture

Carbon dioxide is emitetd by fossil fuel power stations. A traditional power station just releases it into the environment, potentially increasing the enhanced greenhouse effect. _____ is the general term for preventing its release into the environment.

types of charge

positive and negative

charge-coupled devices (CCDs)

used for image capture across a large range of the EM spectum; examples are digital cameras, video cameras, telescopes, and medical X-ray imaging

charged particle scattering experiments

on the atomic scale, charged particles can be scattered by nuclei as a result of the Coulumb repulsion between the charge particle and the nucleus. Energy conservation can be used to determine the closest approach distances and thus estimate the upper limit for the size of a nucleus.

coefficient of volume expansion

the fractional change in volume per degree change in temperature; units are 1/K

combined heating and power systems (CHP)

improve the overall efficiency of electricity generation by utilizing the thermal energy generated to, for example, supply hot water for local domestic supply

components of vecotrs

When a vector is resolved into different direcions, the results are called _____.

compressions

the points on a longitudinal wave where all the particles are 'bunched together' (high pressure)

conductors

a material that allows the flow of charge through it

law of conservation of charge

the total charge of an isolated system of interacting particles always remains the same

law of conservation of linear momentum

the total linear momentum of a system of interacting particles remains constant provided there is not resultant external force (the system is isolated)

constructive interference

When two identical waves meet at point and the waves are exactly in phase, the resulting wave has twice the amplitude of either of the original waves

control rods

movable rods that readily absorb neutrons; they can be introduced or removed from the reaction chamber in order to control the chain reaction

controlled nuclear fission

takes place in power stations; excess neutrons are absored to ensure that the nuclear reactions take place at a constant rate

correlation and cause

two measurements are _____ if there is a statistical/mathematical link between the measurements; two measurements are said to have a casual link if one measurement is related to a factor that causes a change in the second measurement. The fact that two measurements are correlated does not imply that here is a causal link between the two.

Coulomb's law

the electrostatic force between any two point charges masses is proportional the product of the charges and inversely proportional to the square of their distance of separation

centripital acceleration (CPA)

the acceleration of an object moving at constant speed in uniform circular motion. Even though the speed is constant, the direction of the object's velocity is changing all the time, so the object must be accelerating. The resultant force is called _____. Always directed toward the center of the circle.

principle of conservation of energy

energy cannot be created or destroyed; it just changes from one type of energy to another

crest

the peak of a transverse wave (the point of maximum positive displacement)

damping

involves a force that is always in the opposite direction to the direction of motion of the oscillating particle and is a dissipative force (the oscillating particle particle loses energy)

de Broglie equation

all moving particles have a 'matter wave' associated with them; same equation can be used to calculate the momentum associated with photons

decay constant and half-life

ln2/decay constant

decimal numbers

numbers to the base of 10

degraded energy

In any process that involves energy transformations, the energy that is transferred to the surroundings (thermal energy) is no longer available to perform useful work. This unavailable energy is known as _____.

derived unit

a unit that is defined in terms of fundamental units

destructive interference

When two identical waves meet at a point and the waves are exactly (180 degrees) out of phase, the resulting wave has zero amplitude; the two waves cancel each other out

diffraction

the phenomenon of the spreading of a wave after an aperture or obstacle; the process by which wave energy is received in the geometric shadow region after an obstacle or gap; to be noticeable, whte size of the obstacle or gap needs to be the same order of magnitude as the wavelengh; the spreading of sound around corners or the bending of water waves around a harbour wall

diffraction equation for angle of first minimum at a circular aperture

1.22 x wavelength divided by slit width in meters

diffraction equation for angle of first minimum at a single slit

angle equals wavelength divided by slit width

digital

encodes the information using only two possible values (1 or 0)

direction of the force on a current in a magnetic field

perpendicular to the plane that contains the current and the magnetic field; if the current is in the x direction and the magnetic field is in the y direction of a standard graph plotted on a piece of paper, then the force will be out of the paper, in the z direction, as described by Flemming's left-hand rule

direction of the force on a moving charge in a magnetic field

perpendicular to the plane that contains the direction vector of the charge and the magnetic field. If the charge is moving in the x direction, and teh magnetic field is in the y direction of a standard graph plotted on a piece of paper, then fthe force will be our of the paper, in the z direciton, as described by flemming's left-hand rule.

direction of magnetic field

the direciton of th force that would be felt by the north pole of a small test magnet if placed at that point

displacement

the distance from the origin in a particular direction; a vector quantity

Doppler approximation for EM waves

the change in frequency of EM waves as a result of the relative motion between source and observer is given by the following approximation

Doppler effect

a change in frequency of a wave that results from either a moving source of waves, a moving observer, or both.

Doppler effect with a moving source

observed frequency of sound equals frequency of sound measured when there is no relative motion x (speed of sound in still air + speed of observer divided by speed of sound in air)

efficiency

the ratio of useful energy to the total energy transferred, often expressed as a percentage; the ratio of useful power out to toal power in; scalar quantity without units

Eintens equation

plank's constant x frequency of incident EM = work function fo surface in J + maximum kinetic of the emitted photoelectrons

Einstein's mass-energy equivalence relationship

allows us to calculate the energy that is in the form of mass; energy = mass x the square of teh speed of light

elastic collisions

collitions in which no energyis gained or lost; collisions between atoms and molecules

electric field strength

the force per unit charge on a test point charge placed at a point; a vector quantity

electric potential

the difference in electrical energy per unit test charge at that point; electrical energy per unit test charge at that point; the zero of it is taken to be at infinity so it is equal to the work done per unit charge in bringing a small point test charge from infinity to that point; scalar quantity

electric current

rate of flow of charge

electric potential difference

the energy difference per unit charge

electric power dissipation

a device that is the pboduct of the potential difference across it and the current flowing through it

electromagnetic (EM) waves

travel with the same speed in a vacuum

'electron in a box' model

pictures an eletron as being confined to a fixed region in one dimension-the size of a box; Analyses of possible standing-wave patterns for the electron's wavefunction result in only descrete energy levels being available

electronvolt

unit of energy used on the atomic scale; the energy gained or lost by one electron as it moves throught a potential difference of 1 volt

e.m.f.

total energy dissipated per unit charge around a circuit; electromotive force

emission spectra

When an element is hot enough (given enough energy) it emits light. Analysis of this light shows taht eah element emits specific frequencies; these specific frequencies form the electron's _____.

emissivity

the ratio of power radiated per unit area by a given surface to the power radiated per unit area by a black body at the same temperature; has no units

energy

the work that has been done on a body; scalar quantity

energy balance climate model

If the incoming radiation intensity to a planet's surface and its outgoing radiation intensity are not equal, then the planet's temperature will vary as given by temperature change = (incoming radiation - outgoing radiation) x time taken all divided by the surface heat capacity

energy density

the energy liberated per unit mass of fuel consumed; measured in Joules per kilogram

enhanced greenhouse effect

greenhouse effect caused by human activites; possible effect is a rise in sea level; efforts to reduce are Intergovernmental Panel on Climate Change (IPCC), the Kyoto protocol (amendment to UN Framework Convention of Climate Change) and teh Asia-Pacific Partnership on Clean Delelopment and Climate (APPCDC)

entropy

a system property that expresses teh degree of disorder in the system

equation of state for ideal gas

PV=nRT

equipotential surfaces and electrical field lines

electric field lines are always at right angles to equipotential surfaces

expotential surfaces and gravitational field lines

gravitational field lines are always at right angles to equipotential surfaces

error bar

indicates the absolute uncertainty associalted with a point being plotted on a graph; can be in x or y direction or both

escape speed from a planet

the speed that an object needs to have at the surgace of the planet in order to have enough kinetic energy to excape the gravitational attraction of teh planet

evaporation

the process by which induvidual molecules (the faster-moving ones) leave the surface of a liquid and enter the gas pahse; only takes place at teh surface of the liquid at room temperature below the liquid's boiling point

Faraday's law

the magnitude of an induced e.m.f. is proportional to teh rae of change of flux linkage

Lenz's law

the direction of teh induced e.m.f is such that if an induced current were able to flow, it would oppose the change which caused it

first law of thermodynamics (principle of energy conservation)

the energy transferred to the gas from its surroundings equals the increase in the internal energy of the gas + the work done by the gas (in joules)

forced oscillations

It is possible to force a system to oscillate at any frequency by subjecting it to a changing force at that frequency

fractional uncertainty

the ratio between the absolute unertainty and the recorded value

frequency

the number of completed oscillations in a given period of time; measured in hertz

frequency vs. period

Time period = 1/frequency

fuel enrichment

the process by which the isotopic composition of a nuclear fuel is increased to make nuclear fissions more likely; usually unranium fuel rods are _____that the percentage of uranium-235 is increased

fundamental unit

a unit that is defined from first principles

fundimental units in SI units

kilogram; meter; second; ampere; mole; kelvin

gamma radiation

photons of high-energy electromagnetic radiation emitted as a result of a nucleus changing from an excited state into a lower energy state

graviational field strength at a planet's surface

g=G(M/square of r)

gravitational field strength

the force per unit mass on a test point mass placed at that location; a vector quantity

gravitational field strength vs. gravitational potential energy

gravitational field strenght = the difference in gravitational potential x the distance over which the difference in gravitational potential has been measured

gravitational potential difference

the difference in gravitational energy per unit test mass between the points

gravitational potential

gravitational energy per unit test mass at that point; the zero of _____ is taken to be at infinigy so gravitational potential is equal to the work done per unit mass in bringing a small point test point from infinity to that point; a scalar quantity

formula for gravitational potential due to a point mass

gravitational potentail at a fixed difference = -(universal gravitational constant x mass causing the gravitational potential)/(fixed distance away from the mass)

gravitational potential energy

the energy that a body has as a result of its position in a gravitational field; a scalar quantity

greenhouse effect

The atmosphere is transparent to many frequencies of electromagnetic radiation. Much of the power received from the Sun is in the visible and ultraviolet regions. This causes the surface of the Earth to warm up and radiate in the infrared. Some of this infrared radiation is absorbed by gases in the atmosphere, causing the atmosphere to warm up, and re-radiated in all directions; the net effect is that the atmosphere and the surface of the Earth are warmed.

greenhouse gas

gases in the atmosphere that absorb infrared radiation radiated from Earth; include methane, water vapor, carbon dioxide, and nitrous oxide; also ozone and chorofluorocarbons

heat exchanger

allows the nuclear reaction to toccur in a place that is sealed off from the rest of the environment; the reactions increase the temerature in the core; this thermal energy is trnasferred to heat water, and the steam that is produced turns the turbines

hybrid vehicles

uses electric motors with a petrol engine as back-up to provide additional power when necessary; sophisicated computerized wtstems switch from the electric motor to the petrol engine and back as required

hydroelectric schemes

use gravitational potential energy of water to generated electrical energy

ideal ammeter

has zero resistance; connected in series at the point where the current needs to be measured

ideal gas

a gas where newton's laws apply to molecular behaviour, there are no intermolecular forces (except in collisions), molecules ar treated as points; molecules are in random motion; the collisions between the molecules are elastic; no time spent in collisions; cannot be liquified

real gases

show deviations from the equation of state for ideal gases; can approximate to ideal gas behaviour at low pressures

ideal transformer (step-up and step-down)

changes the voltage of an alternating current (AC) input without any loss of energy. If the output voltage (on the secondary) is greater than the input voltage (on the primary), it is known as a step-up transformer. If the output energy (on the secondary) is less that the input voltage (on the primary), it's a step-down transformer.

ideal voltmeter

has infinite resistance; connected in parallel between the two points where the potential difference needs to be measured

impulse

the product ot the resultant force acting on the object and the time for which this force acts; equatl to change of momentum of the object; vector quantity

induction

happens in e.m.f. whenever there is a relative motions between the conductor and a magnetic field (whenever magnetic lines of flux are cut; takes place whenever there is a time-changing magnetic flux passing through a coil of wire

inelastic collisions

collisions in which the objects involved in the collision lose energy; all lab. collisions

instantaneous

value at one particular instant of time

insulator

a material tht does not allow the flow of charge through it

intensity

the power per unit area that is received by the observer; related to amplitude of the wave; intensity=power received/area

internal energy

total potential and random kinetic energy of the molecules of the substance

internal resistance of a battery

the effective extar resistance that is added to a circuit by the battery

isobaric

a change that takes place at constant pressure

isochoric (isovolumetric)

change that takes place at a constant volume

isothermal

change that takes place at constant temperature

isotopes

nuclides that contain the same number of protons (so the same element) but different number of neutrons

Kelvin scale of temperature

has the same unit step as the Celsius temperature scale, but the zero of the _____ is at absolute zero

Kepler's third law

the cube of the average radius of orbit of a planet is proportional to the square of that planet's orbital time period

kinetic energy

the energy that a body has as a result of motion; scalar quantity

least-significant bit

the bit representing 2^0 and is the furthest on the right when the binary number is written down

light dependent resistors (LDR)

a device whose resistance depends on the amount of light shining on its surface; an increase in light causes a decrease in resistance

linear momentum

the procuct of an object's mass and its velocity; a vector quantity

longitudinal waves

involve oscillations that are in the same directon as the direction of energy transfer; sound waves are an example

magnetic fields

moving charges give rise to _____

magnetic flux

the magnetic field strength x the area under consideration x the angle between the magnetic field and the normal to the surface

magnification

the ratio of the length of the image on the CCD to the length of the object

Malus' law

intensity of the transmitted light = intensity of the incident light x cos^2 of the angle between the plane of vibration and the analyser's preferred direction

mass deflect

the mass of any nucleus is less than the mass of the component nucleons that go to make it up. The difference between the mass of a nucleus and the masses of its component nucleons is called the mass deflect

moderator

in a nuclear reactor, it is there to slow down emitted neutrons; collisons between the fast-moving neutrons and the nuclei of the moderator slow them down and allow further nuclear reactions to take place

molar mass

the mass of one mole of a substance; if an element has a certain mass number, A, then the _____ will be A grams

mole

the basic SI unit for amount of substance; equal to the amount of that substance that contains the same number of atoms as 0.012 kilograms of Carbon-12

most-significant bit

the bit representing the highest power of 2 and is the furthest on the left when the binary number is written down

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