A-Level Physics OCR A Definitions

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negative temperature coefficient (NTC)

A relationship in which variable decreases as temp increases NTC Thermistors

Mass

Amount of matter, a base quantity kg

angle of incidence

Angle between direction of travel of incident ray and normal

ampère

Base SI unit of electric current, A, current flowing in two parallel wires in a vacuum 1m apart such that atractive force 2.0*10-7 per metre length of wire between them

Ammeter

Device used to measure electric current-placed in series (ideally 0 resistance)

led

Diode that emits light when it conducts electricity

air resistance

Drag/resistive force experienced by objects moving through air

conservation of charge

Law where electric charge can neither be created nor destroyed-total charge must be same before and after interaction

radio waves

Long wavelength electromagnetic waves >10-1m

amplitude

Max displacement from equlibrium point of a particle in a wave

number density

Number of free electrons per cubic metre of material, symbol n, unit m-3

projectile

Object that is thrown or propelled on surface of earth

Primary Waves(P-Waves)

Primary waves- longitudinal waves that travel through Earth earthquakes

kelvin

SI Base unit of temperature

antiparallel

Same line but opposite directions

S-Waves

Secondary transverse waves that travel through Earth from an earthquake

X-rays

Short wavelength electromagnetic wave 10-8m to 10-13m used medical imaging

Principle of conservation of energy

Total energy of closed system remains constant-cannot be created/destroyed

potential divider equation

Vout=(R2/(R1+R2))xVin

turn-ratio equation

Vs/Vp = ns/np = Ip/Is

principle of superposition of waves

When 2 waves of same type meet at a point in space, their resultant displacement is the sum of their individual displacements

Kirchhoff's first law

at any point in electrical circuit, sum of currents into that point is equal to sum of currents out of that point. Electrical charge is conserved

ion

atom has either lost of grained electrons so has net charge

proton number

atomic number = no protons in nucleus

half-life

average time takes for half no active nuclei in a sample of an isotope to decay

mean drift velocity

average velocity of electrons as they move through a wire, symbol v, unit ms-1

loading(electrical)

connecting component across terminals of source of e.m.f or across another component

molar gas constant

constant in equation of state of ideal gas 8.31JK-1mol-1

Stefan constant

constant in stefans law L=4pir^2iotaT^4 luminosity of star to its surface area and absolute surface temperature

terminal velocity

constant speed reached by an object when drag force is equal and opposite to the weight of the object

exponential decay

constant-ratio process in which quantity decreases by same factor in equal time intervals

excited

containing an electron of electrons that have absorbed energy and boosted into higher energy level

brownian motion

continous random motion of small particles suspended in a fluid visible under microscope

standard model

current theory of particle physics quarks and electrons

heavy damping

damping that occurs when damping forces are large and period of oscillations increases slightly with rapid decrease in amplitude

light damping

damping that occurs when damping forces are small and period of oscillations is unchanged

attenuation

decrease in intensity of em radiation as passes through matter of space

white dwarf

dense star formed from core of red giant

volt

derived SI unit of P.D. and e.m.f. V. Energy transferred per unit charge. 1V is p.d. across componenet when 1J of energy transferred per 1C passing through component

coulomb

derived SI unit of electric charge, 1 coulombs passes a point in one second. 1C=1As

ohm

derived SI unit, Ω, resistance of component that has P.D of 1V per unit Ampere

kilowatt-hour

derived unit energy-1kWh=3.6MJ. Energy in kWh can be calculated by multiplying power by time

electronvolt

derived unit of energy-subatomic particles and photons. Energy transferred to/from electron when passes through P.D of 1V. 1eV = 1.6*10-19

I-V characteristic

description of relationship between electric current in component and p.d. accross it. I again V graph

cloud chamber

detector of ionising radiation vapour at low temp where liquid condenses around ionised particles

electricity meter

device that measures electrical energy supplied in kWh to a house from the grid

cell

device that transfers chemical energy into electrical energy

electron gun

device that uses accelerating potential difference to produce beam of electrons

ultrasound transducer

device used to generate and recieve ultrasound converts elec to sound and sound to elec

voltmeter

device used to measure p.d. must be in parallel and would have ideally infinite resistance

gold leaf electroscope

device with metallic stem and gold leaf used to measure electric charge used to be used as voltmeter for high voltages

phase difference

difference between displacements of particles along a waves. Degrees or radians.

mass defect

difference between mass of nucleus and mass of completely separated constituent nucleons

phase difference

difference in displacement between 2 oscillating objects identical adjacent points or displacement of oscillating object at different times

path difference

difference in distance travelled by 2 waves from source to specific point

right hand grip rule

direction field from direction which fingers right hand curl around wire

Lenz's law

direction of induced emf or current is always such as to oppose the change producing it

energy level

discrete amount of energy that electron within atom is permitted to possess

displacement (waves)

distance from equilibrium position in particular direction

light-year

distance travelled by light in a vacuum in a time of 1 year 9.46x10^15m

braking distance

distance travelled by vehicle from time brakes applied to full stop

thinking distance

distance travelled by vehicle from when driver sees reason to stop to when brakes applied

wave speed

distance travelled by wave per unit time

displacement

distance travelled in particular direction-vector with magnitude and direction

parsec

distance which radius of one AU subtends an angle of one arcsecond

Maxwell-Boltzmann distribution

distribution of speed of particles in a gas

resistance

dividing potential differnce across it by current in it Ohms

potential divider

electrical circuit designed to divide p.d. across 2 or more components to produce specific output

filament lamp

electrical component containing filament of wire converting electrical to light

resistor

electrical component that obeys ohms law

thermistor

electrical component which resistance that decreases as temperature increases(Negative temperature Coefficient)

potentiometer

electrical component with 3 terminals which can change p.d. between 2 terminals

ultraviolet

electromagnetic wave with wave length 4x10-7 to 10-8

microwaves

electromagnetic wave with wavelengths 10-1m to 10-3m

infrared waves

electromagnetic waves with wavelengths 10-3m to 10-7m

visible light

electromagnetic waves with wavelengths 4x10-7m to 7x10-7m

free electron

electron in metal not bound to atom-delocalised

photoelectrons

electrons emitted from surface of metal by photoelectric effect

neutron

elementary neutral particle hadron found in nucleus of atoms

quark

elementary particle exist in 6 forms and joins quarks to make hadrons

thermionic emission

emission of electrons from surface of hot metal wire

photoelectric effect

emission of photoelectrons from metal surface when electromagnetic radiation acts on metal

kinetic energy

energy associated with object as result of its motion

ground state

energy level with most negative possible value for electron within atom

specific heat capacity

energy required per unit mass to change the temperature by 1K measured jkg-1K-1

specific latent heat

energy required to change phase per unit mass while at constant temp

specific latent heat of vaporisation

energy required to change unit mass of substance from liquid to gas while at const. temp

specific latent heat of fusion

energy required to change unit mass of substance from solid to liquid while at const. temp

elastic potential energy

energy stored in a object due to its deformation

tensile force

equal and opposite forces acting on a material to stretch it

de Broglie equation

equation relating wavelength and momentum of a particle

grating equation

equation used to determine wavelength of monochromatic light sent through diffraction grating

x-ray tube

equipment that produces x ray photons by firing electrons from cathoded ray across large pd in evacuated tube, a ray photons produced when electrons decellerated hitting target metal of anode

velocity selector

everything that exdevice uses elec and magnetic fields to select charged particles of velocity by deflection

red giant

expanding star at end of its life with inter core where fusion no longer takes place but fusion of lighter elements continues in outer shell

tensile strain

extension per unit length (ratio no units)

Optical Fibre

fibre made of glass designed with verying refractive index to internally reflect pulses of light through it

gravitational field

field created around any object with mass extending to infinity but dinishing as mass further from centre of mass

node

for a stationary wave, a point where amplitude is always 0

principle of moments

for body in rotational equilibrium, sum anticlockwise equals sum of clockwise on same point

triple point

for substance, specific temp and pressure where all 3 phases of substance exist in thermodynamic equilibrium

force-extension graph

force against extension with area under graph=work done on material

Hooke's law

force applied is directly proportional to extention of spring unless limit of proportionality is exceeded

Newton's law of gravitation

force between 2 point masses is directly proportional to product of masses and inversely to square of separation between them F = Gm1m2/r2

normal contact force

force exerted by a surface on an object which acts perpendicular to the surface

pressure

force exerted per unit cross sectional area. Pascals

gravitational field strength

force exerted per unit mas at point within gravitational field

electric field strength

force experience per unit positive charge at that point

tensile stress

force per unit cross-sectional area Pa

restoring force

force that tries to return system to equilibrium position

centripetal force

force which keeps body moving with constant speed in circular path

natural frequency

frequency of free oscillation

driving frequency

frequency where periodic driver force applied to system in forced oscillation

electromagnetic spectrum

full range of frequencies of electromagnetic waves

elementary particle

fundamental article

lepton

fundamental particle or antiparticle that is not affected by strong nuclear force

aphelion

furthest point from sun in orbit

coupling gel

gel with acoustic impedance similar to skin gel used in ultrasound

Hubble constant

gradient of line of best fit for recessional speed against distance from earth

force-time graph

graph of net force against time, area under graph = to impulse

wave profile

graph showing displacement of particles in wave against distance along wave

Hertzsprung-Russell diagram

graph showing relationship between luminosity of stars and average surface temp

uniform gravitational field

gravitational field in whcih field lines are parallel and value for g remains constant

weight

gravitational force on an object N newtons

Planck constant

h, .63x10-34Js

baryon

hadron made with combination of 3 quarks

infalction

hase of acceleration of expansion of universe

protostar

hot dense sphere of condensing dust and gas on way to becoming star

red supergiant

huge star in last stages of life before explodes in supernova

oscilloscope

instrument that displays electrical signal as voltage against time

ionic solution

ionic compound dissolved in liquid to form electrolyte

beta radiation

ionising radiation consisting of fast moving electrons

gamma radiation

ionising radiation consisting of high energ photons wavelength 10^-13m at c

alpha radiation

ionising radiation of 2 proton 2 neutron particles

comet

irregular body of ice, dust and rock in highly eccentric orbit around sun

plastic deformation

irreversible change in shape of object due to compressive/tensile force

closed system

isolated system that has no interaction with surroundings

brittle

lack of ability of plasticity

gas laws

laws governing behaviour of ideal gases like Boyles law

red shift

lengthening of observed wavelength occurs when wave source moving away red-shifted

neutrino

lepton that carries no charge with minute mass less that millionth of electron

monochromatic light

light of a single frequency

spectral line

line in an emmision line soectrum or absorption line spectrum at specific wavelength

wavefront

line of points in phase with each other in a wave perpendicular to direction of energy transfer

isotherm

line on pressure volume graph connecting points of same temperature

Kepler's second law of planetary motion

line segment connecting planet to the sun sweeps out equal areas during equal intervals of time

gravitational field lines

lines of force used to show grav. pattern of object

electrolyte

liquid containing ions that are free to move so conduct electricity

hysteresis loop

loop shaped plot obtained when loading or unloading material produces different deformations

fundamental frequency

lowest frequency at which object can vibrate

absolute zero

lowest possible temp when substance has min internal energy

faradays law

magnitude of induced emf directly proportional to rate of cange of magnetic flux linkage

main sequence

main period of stars life during which it is stable

fiducial marker

marker for a point used as fixed basis for measurement of comparison

rest mass

mass of object such as particle when stationary

molar mass

mass of one mole of substance

Chandrasekhar limit

mass of stars core which electron degeneracy pressure sufficient to prevent gravitational collapse 1.44 solar masses

density

mass per unit volume of a substance

polymeric

material of long chain molecules-rubber

semiconductor

material with a low number density than a typical conductor

strong material

material with large value for ultimate tensile strength

trough

max negative amplitude of a transverse wave

ultimate tensile strength

max stress that material can withstand before breaks

peak

maximum positive amplitude of a transverse wave

astronomical unit

mean distance from earth to sun 150 million km

mean square speed

mean of squaraed velocities of particles in a gas

attenuation coefficient

measure of absorption of x ray photons by substance

amount of substance

measure of amount of matter in moles

eccentricity

measure of elongation of ellipse

relative charge

measurement of electric charge of particle in multiples of elementary charge

target metal

metal with high melting point used for anode in X-ray tube

carbon dating

method for determining age of organic material activites of carbon 12 and 14 nuclei of material

crystallography

method for determining structure of substance by studying interference patterns produced by waves passing through a crystal of substance

microwave background radiation

microwave signal of uniform intensity detected from environment fits profile for black body at temp 2.7K

escaoe velocity

min velocity which object has just enough energy to leave specified grav. field

wavelength

minimum distance between 2 identical adjacent points on a wave

work function

minimum energy needed to remove single elctron from surface of particular metal J

binding energy

minimum energy required to seperate nucleus into consistent protons and neutrons

threshold frequency

minimum frequency of the electromagnetic radiation that will cause the emission of electron from surface of a metal Hz

threshold voltage

minimum potential difference at which diode begins to conduct

arcminute

minute of arc 1degree=60 arcminutes

ideal gas

model of gas including assumptions that simplify behaviour

kinetic model

model that describes all substances made of atoms, ions or molecules arranged differently depending upon phase

conventional current

model used to describe electric current in a circuit-conventional current travels from positive to negative-but doesnt actually

Boltzmann constant

molar gas constant divided my avogadro constant-mean kinetic energy of atoms in gas to temperature

constant speed

motion in which distance per unit time is same

free oscillation

motion of mechanical system displaced from equilibrium position then allowed to oscillate without any external forces

free fall

motion of object accelerating under gravity with no other force acting

constant velocity

motion where change in displacement per time stays same

rarefaction

moving region which medium is less dense or has less pressure than surrounding medium

refractive index

n=c/v where c is speed of light and v is speed of light through material

cathode

negatively charge electrode

anion

negatively charged ion -attracted to anode

electron degeneracy pressure

pressure created by electrons in core of collapsing star due to Pauli exclusion principle

radiation pressure

pressure from photons in core of star acts outwards to counteract pressure from gravity pulling inwards

boyle's law

pressure of ideal gas inversey proportional to volume provided mass and temp do not vary

gas pressure

pressure of nuclei in stars core pushing outwards counteracting grav. force pulling matter into star

decay constant

prob of decay of individual nucleus per unit time

fusion

process in 2 smaller nuclei join

fission

process where large nucleus splits into 2 smaller after absorbing neutron

radioactivity

process which unstable nuclei split, decay emitting ionizing radiataion alpha beta or gamma

time constant

product of capacitance and resistance for capacitor resistor circuit-time taken for PD to decrease to e^-1 of initial value when capacitor discharges through resistor

magnetic flux

product of component of magnetic flux density perpendicular to a given area and that cross-sectional area: ∅=BAcosθ

acoustic impedance

product of density of substance and speed of ultrasound

work

product of force and distance moved in direction of force J

moment

product of force and perpendicular distance from a pivot or stated point

magnetic flux linkage

product of number of turns in coil and magnetic flux density Weber turns

torque

product of one of forces in couple and perpendicular distance between forces

piezoelectric effect

production of emf by crystals when compressed, stretched twisted or distorted

ductile

property of a material that has large plastic region in a stress-strain graph

resistivity

property of material measures in Ohms

linear momentum

property of object travelling in straight line. Mass * velocity

tension

pulling force exerted by a string, cable or chain on an object

force

push or pull on object N

force constant

quantity for dividing force by extension for object obeying hookes law

derived quantity

quantity that comes from base units

vector quantity

quantity with magnitude and direction

photon

quantum of electromagnetic energy-photon energy E is E=hf where h is planck constant f is frequency of electromagnetic radiation

intensity(waves)

radiant power passing through surface per unit area

corrected count rate

radiation count rate measured in experiment minus background

background radiation

radiation emitted by surrounds

radiopharmaceutical

radioisotope chemically combined with elements that will target tissues to ensure radioisotope reaches correct organ or tumor

angular velocity

rate of cange of angle for moving object in circular path

average velocity

rate of change of displacement in time

Newtons Second Law of motion

rate of change of momentum of an object is directly proportional to the resultant force in direction of force

activity

rate of nuclei decay in radioactive source becquerels

Young modulus

ratio of tensile stress to tensile strain when these quantities are directly proportional to each other Pa

intensity reflection coefficient

ration of reflected intensity over incident intensity for ultrasound incident at boundary

efficiency

ration of useful output energy to total input energy (%)

chain reaction

reaction where neutrons released trigger exponential growth in rate of reactions

hubbles law

recessional speed v of galaxy is directly proportional to its distance from earth

nucleus

small positive charged region in centre of atom where most mass concentrated

elementary charge

smallest sum of electric charge. 1.6*10-19

quantisation

some quantities sucha s energy or charge are made of lumps of base quantities

wave source

source waves object moving to relative view causes doppler effect

continuous spectrum

spectrum where all visible frequencies or wavelengths are resent

instantaneous speed

speed at moment it is measured-speed over infinitely small time interval

Kepler's third law of planetary motion

square of orbital period T of planet is directly proportional to cube of its average distance from the sun

root mean square speed

square root of mean square speed

thermal equilibrium

state where no net flow of thermal energy

magnetic flux density

strength of magnetic field F/IL where F force acting on current carrying conductor placed at right angles to magnetic field, I is current in conductor L is Length of conductor in magnetic field Symbol B unit Tesla T

breaking strength

stress value at point of fracture-breaking force diveded by cross sectional area

plumb-line

string with weight used to provide vertical reference line

fluid

substance that can flow-liquids and gases

coolant

substance that removes thermal energy from reactors

moderator

substance used to slow down fast neutrons produced in fission reactions so they propagate fission reaction

internal energy

sum of randomly distributed kinetic and potential energies of atoms, ions or molecules within substance

interference

superposition of 2 progressive waves from coherent sources to product a resultant wave with displacement equal to sum of indiv. displ. of waves

destructive interference

superposition of 2 waves in antiphase so the waves cancel each other out and resultant wave has smaller amplitude than original waves

constructive interference

superposition of 2 waves in phase so resultant wave has greater amplitude than original waves

radial field

symmetrical field that diminished with distance^2 from centre

spectroscopy

technique in physics that uses spectral lines to identify elements present in others

stellar parallax

technique used to determine distance of starts by conparing apprent distances again itself 6 months apart-wobble

celsius scale

temp scale 100 degrees between freezing point and boiling of water

acceleration

Rate of change of velocity. Vector quantity

power

Rate of work done Watts

planetary nebula

outer layers of red giant drifted into space leaving core behind at centre as white dwarf

superposition

overlap of 2 waves at a point in space

equation state of ideal gas

pV=nRT where n is no moles of gas

couple

pair of equal but opposite forces acting on a body but not in straight line

scintillator

part of gamma camera from sodium iodide which produces thousands of photons of visible light when struck by single gamma photon

collimator

part of gamma camera, thin tubes of lead absorbing photons arriving at angle to axis of tubes so picture obtained

nucleon

particle in nucleus of atom either proton or neutron

hadron

particle of antiparticle affected by strong nuclear force

fundamental particle

particle that has no internal structure and cannot be split into smaller particles

charge carrier

particle with charge that moves through material to form electric current

in phase

particles oscillating perfectly in time and position with each other

out of phase

particles that are neither in phase or antiphase are out of phase

interference pattern

pattern of constructive and desctructive interference formed as waves overlap

wlen's displacement law

peak wavelength at which intensity of radiation from black body is maximum is inversly proportional to absolute temp of black body

phase

phase of matter in state

diffreaction

phenomenon of waves passing through a gap or around an obstacle spread out

solar system

planetary system of star and at least one planet in orbit

diffraction grating

plastic slide with spacings that diffract visible wavelengths of light

pivot

point about which body can rotate

maximum waves

point of greatest amplitude on interference pattern from constructive interference

minimum(waves)

point of least amplitude in interference pattern, produced by destructive interference

yield point

point on stress strain graph beyond where deformation is no longer entirely elastic

centre of mass

point through which any fexternal force applied makes straight line motion but no rotation

cation

posiively charge ion that is attracted to cathode

proton

positively charged particle, hadron found in nucleus of atoms

terminal p.d.

potential difference across a electrical power source-when there is no current, this is equal to e.m.f of power source but if current the source is equal to e.m.f - lost volts

Archimedes' Principle

Upthrust on a object in fluid equals weight of fluid it displaces

Ohms Law

V is directly proportional to I provided KEPT AT CONSTANT TEMPERATURE

upthrust

upward bouyant force exerted on a body immersed in fluid

impedance matching

use of 2 substances with similar acoustic impedance to minimise reflection

wave equation

v=fλ where v = speed, wavelength = λ and f = frequency

elastic limit

value of stress or force beyond which elastic deformation becomes plastic deformation-object will not return to original shape or size after force released

limit of proportionality

value of stress or force beyond which stress is no longer directly proportional to strain

velocity

vector quantity equal to rate of change of displacement

Doppler equation

velocity of observed over light

fundamental mode of vibration

vibration at fundamental frequency

magnetic field pattern

visual representation of direction and strength of magnetic field

longitudinal wave

wave in which medium is displaced in same line as direction of energy transfer-oscillation of medium particles are parallel to direction of energy transfer

transverse wave

wave in which medium is displaced perpendicular to direction of travel of wave

stationary wave

wave that remains in constant position with no net transfer of energy and is characterized by its nodes and antinode

standing wave

wave that remains in constant position with no net transfer of energy and is characterized by its nodes and antinodes

progressive wave

wave which peaks and troughs/compressions and rarefractions move through medium as energy is transfered

equilibrium

when body in equilibrium, net force and moment acting are 0

superconductivity

where resistivity of material falls to almost 0 when material is cooled below certain temperature

harmonic

whole number multiple of fundamental frequency

electric potential

work done by external force per unit positive charge to bring charge from infinity in field

electromotive force (e.m.f)

work done on charge carriers per unit charge (V) measured accross a cell, battery or power supply

gravitational potential

work done per unit mass to bring object to point in grav field

photomultiplier tube

apparatus that converts photon of visible light to electrical pulse

electric charge

(Q)physical property + or - measured in coulombs C

impulse

area under force time graph-product of force and time for which force acts

series

arrangement of electrical components connected end to end meaning current is same in each component

compressive force

2 or more forces acting together that reduce length of volume of object

resistor circuit

2 or more resistors arranged to provide specific reisstance

acoustic matching

2 substances with similar acoustic impedance to minimise reflection of ultrasound at boundary

triangle of forces

3 forces acting at a point in equilibrium

Abogadro constant

6.02*10^23 no atoms in 12g of carbon 12

Newtons First Law of motion

A body will remain at rest or continue to move at constant velocity unless acted upon by a resultant force

scalar quantity

A quantity with magnitude but no direction

Newtons Third Law of motion

Body A acting on body B exerts an equal but opposite for to Body B acting on Body A

cosmological principle

assumption that universe is homogeneous and isotrophic

normal

Imaginary line perpendicular to a surface such as boundary between one medium and other

Kirchhoff's second law

In a closed loop of an electrical circuit, sum of e.m.f.s is equal to sum of p.d.s

magnetic field lines

Lines of force drawn to represent a magnetic field pattern

average speed

Rate of change of distance in time

lost volts

P.D accross inernal resistor of source of e.m.f

antiphase

Particles ocillating where one reaches max displ. whilst other reaches min displ.

Maximum (waves)

Point of greatest amplitude in a interference pattern, produced by constructive interference

Acceleration of free fall

Rate of change of velocity of object falling in a gravitational field

medical tracer

compound labelled with radioisotope traced inside body using gamma camera

SI

Systeme International d'Unites

potential difference

Work Done per unit charge through component

non-ohmic component

a component that doesn't obey ohms law e.g. filament lamp or diode

compression

a region in which medium is denser or has higher pressure than surrounding medium

stiffness

ability of an object to resist deformation

absorption coefficient

absorption of x ray photons by substance atenuation coefficient

centripetal acceleration

acceleration of any object travelling in circular path at constant speed. Always acts towards centre of circle

mass

amount of matter measure in kg

mole

amount of substance that contains elementary entities as atoms 0.012kg of carbon 12

angle of reflection

angle between direction of travel of reflected ray and normal

law of reflection

angle of incidence = angle of reflection

critical angle

angle of incidence at boundary between 2 media will product an angle of refraction of 90 degrees

Parallax angle

angle of shift in position of relatively close star again backdrop of more distnace starts due to orbit-wobble

antiparticle

antimatter counterpart of particle with opposite charge to particle and same mass

positron

antiparticle of electron

ionising radiation

any form of radiation that can ionise atoms by removing an electron to leave a positive ion

meson

any hadron comprising of combo of quark and anti-quark

Coulombs law

any two point charges exert electrostatic force on each other directly proportional to product of charges and inversely to square of their seperation

binding energy per nucleon

binding energy divided by no protons/neutrons in nucleus-greater binding, more tightly bound to nucleus

planetary satellite

body in orbit around planet

satellite

body orbiting around planet

energy

capacity for doing work Joules

GPE

capacity for object doing work as result of objects position in gravitational field

refraction

change in direction of wave as it changes speed when passes from one medium to another

reflection

change in direction of wave at boundary between 2 different media so wave remains in same medium

Doppler effect

change in frequency and wavelength of waves received from object relative to observer

compressive deformation

change in shape of object due to compressive forces

tensile deformation

change in shape of object due to tensile forces

gradient

change in vertical axis quantity divided by corresponding change in horizontal axis quantity

capacitance

charge stored er unit potential difference across capacitor

perihelion

closest point to sun in orbit

nebula

cloud dust/gas hundreds size of galaxy

battery

collection of cells that transfer chemical energy to electrical energy

galaxy

collection of stars or dust bound together by mutual gravitational force

inelastic collision

collision in which kinetic energy is lost

perfectly elastic collision

collision where no kinetic energy is lost

capacitor

compenent that stores charge, consists of 2 plates seperated by an insulator

annihilation

complete destruction of article and antiparticle releasing energy in form of photons

dark energy

hypothetical form of energy that neither emits nor absorbs light

expanding universe

idea that space and time always expanding

centre of gravity

imaginary point at which entire weight of object appears to act

supernova

implosion of red supergiant at end of life which leads to ejection of stellar matter into space leaving invert core

resonance

increase in amplitude of forced oscillation when driving frequency matches natural frequency of oscillating system

extension

increase in length of object when tensile force exerted

thermal neutron

neutron in fission reactor with mean kinetic energy similar to therman energy of particles in reactor

frequency

no complete oscillations per unit time

induced fission

nuclear fission when nuclear becomes unstable on absorbing another particle

isotopes

nuclei of same element that have same atomic number but different nucleon numbers

daughter nucleus

nucleus formed following radioactive decay

atomic number

number of protons in nucleus

frequency(waves)

number of wavelengths passing a point per unit time

planet

object in orbit around star with mass large enough for gravity to give round shape. Undergoes no fusion reactions and has cleared its orbit of most other objects

black body

object that absorbs all electromagnetic radiation or when in thermal equilibrium emits distribution of wavelengths at specific temerature

black hole

object which has escape velocity greater than speed of light so not even photons can escape

weak nuclear force

one 4 fundamental forces in nature for inducing beta decay in unstable nuclei

atomic mass unit

one atomic mass unit is 1/12 mass of neutral carbon 12 atom

strong nuclear force

one of 4 fundamental fforces in nature acting on hadrons holding nuclei together

base unit

one of 7 units that form building blocks of SI measurements

negative (charge)

one type of electric charge, like repel, dislike attract

Kepler's first law of planetary motion

orbit of planet is ellipse with sun at one of the two foci

simple harmonic motion

oscillating motion where acceleration of object is directly proportional to its displacement but in opposite direction a=w^2x

damping

oscillation damped when external force acts on oscillato has effect of reducing amplitude of oscillations

forced oscillation

oscillation where periodic driver force applied to oscillator

polarisation

oscillations of transverse waves limited to one plane

isochronous oscillator

oscillator that has same period regardless of amplitute

angular frequency

oscillatory motion-frequency times 2pi

total internal reflection

reflection of all light hitting a boundary between 2 media back into original medium when light is travelling through medium with higher refractive index, incident angle is greater than critical angle

internal resistance

reistance of a source of e.m.f.-causes loss in energy/voltage as charge passes through source

neutron star

remnant core of massive star gone supernova collapsed under own gravity due to high density entirely neutrons

oscillating motion

repetitive motion of object around equilibrium position

pair production

replacement of single photon with particle and antiparticle of same total energy

free-body diagram

represents all forces acting on single object

LDR

resistance decreases as light intensity incident on it increases

drag force

resistive force exerted by a fluid on an object moving through it

equilibrium pos (waves)

resting position for particles in medium

elastic deformation

reversible change in shape of object due to compressive or tensile force-removal of stress or force will return the object to original shape and size

control rods

rods made of material whose nuclei absorb neutrons

conical pendulum

rotates in circle at constant speed

isotropic

same in all directions

geostationary satellite

satellite that remains in same pos relative to spot on earths surface-orbit 24 hours

absolute scale of temperature

scale for measuring temp based on absolute 0 and triple point of water Kelvin

arcsecond

second of arc 1arcminute=60 arcseconds

diode

semiconductor component that allows current only in one direction

grating spcing

seperation between adjacent lines or slits in diffraction grating

emission line spectrum

set of specific frequencies of em radiation visible as bright lines on spectroscope

absorption line spectrum

set specific frequencies of em radiation visible as dark lines on spectroscopy. Absorbed by atoms as electrons excited between energy states by absorbing corresponding amount energy inform of photons

gamma rays

short-wavelength electromagnetic waves *10-10m to *10-16m

blue shift

shortening of observed wavelength tat occurs when wave source moving towards observer

big band

theory that all matter was contained in sigularity

wave particle duality

theory that states that matter has both particle and wave properties and electromagnetic radiation has wave and particulate nature

polycrystalline graphite

thin layers of graphite with regularly arrange carbon atoms in different orientations

timebase

time interval represented by one horizontal square on oscilloscope screen

period(waves)

time taken for one complete wavelength to pass a given point

period

time taken to complete one full oscillation

stopping distance

total distance travelled from when driver sees reason to when vehicle stops. Sum of thinking distance and braking distance

principle of conservation of momentum

total moment of a system remains same before and after a collision or explosion

luminosity

total radiant power output of a star L Watts

step-down transformer

transformer with fewer turns on secondary than on primary

step-up transformer

transformer with more turns on secondary that primary and higher output voltage than input

partially polarised

transverse wave in which more oscillations in one plane that rest, but not fully plane polarised

plane polarised

transverse wave in which oscillations are limited to one plane

unpolarised

transverse wave where oscillations occur in many planes

vector triangle

triangle constructed to scale to determine resultant of 2 vectors

coherence

two waves that are coherent have same constant phase difference

parallel circuit

type of branching electrical circuit where more than one path for current. P.D. is constant I splits up

polarity

type of charge or orientation of cell relative to a component

positive

type of electric charge, pos attract neg. repel other pos

series circuit

type of electrical circuit where components are connected end to end

homogeneous

uniform in terms of distribution of matter across universe

becquerel

unit of activity-one decay per second


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