physics paper 1 keywords

Random error

error is caused by unpredictable fluctuations that affect measurements differently each time.

strong nuclear force

force between nucleons

systematic error

Error consistently affects results in the same way each time

weak nuclear

force causes change in nucleus

precision

closeness of repeated measurements to each other.

electromagnetic force

force between charged particles

repeatability

same experimenter obtains consistent results under the same conditions

gravity

force between masses

reproducibility

different experimenters obtain consistent results under similar conditions

what is conserved in decays/interactions

energy, momentum, baryon, lepton strangeness

resolution

smallest detectable change in a measurement.

how a strange particles produced and decay

produced by the strong and decay by the weak

accuracy

closeness of a measurement to the true or accepted value

strangeness

quantum number assigned to strange particles

when does nuclear instability occur

Too many/few neutrons and too many protons. Excess energy. Electrostatic repulsion between protons

how is strangeness conserved

conserved in strong but changes by +-1 in weak interactions

Pair production

A photon creates a particle and anti particle

threshold frequency

minimum frequency needed to emit electrons from surface of material

Annihilation

A particle and its antiparticle convert into two gamma photons

work function

minimum work done required to remove an electron from surface of metal

beta minus decay

neutron turns into a proton releasing an electron and a anti-electron neutrino

stopping potential

minimum potential needed to stop photoelectric emission

Hadrons

particles that experience the strong interaction

Line emission spectra

When electrons de-excite, they emit photons with specific frequencies. These frequencies form bright lines on a dark background

baryons

protons and neutrons held together by gluons

leptons

electrons, muons, neutrinos

Mesons

pions, kaons, held together by gluons

line absorption spectra

When white light passes through a cool gas, electrons absorb specific frequencies to excite. These absorbed frequencies appear as dark lines on a continuous spectrum.

progressive wave

wave transfers energy from one point to another without transferring matter

coherent source

same frequency with a constant phase difference

phase difference

difference in the positions of two points in a wave cycle

path difference

difference in distance between two wave sources to an interference fringe

material dispersion

Different wavelengths travel at different speeds

modal dispersion

Light rays take different paths, causing arrival delays.

absorption(optical fibres)

impurities in optical fibres lead to light energy getting absorbed leading to signal loss

equilibrium

net force is zero and sum of CM= sum of ACM

terminal speed

drag force = weight

newtons 1st law

object will either stay at rest or move with constant velocity

newtons 2nd law

F=MA and net force is directly proportional to rate of change in momentum

newtons 3rd law

for every action there is an equal and opposite reaction

plastic deformation

permanent change in shape or length of a material after the force is removed

brittle behaviour

material breaks or fractures suddenly with little or no plastic deformation when stress is applied

elastic

momentum and kinetic energy conserved

inelastic

momentum conserved and kinetic energy lost

kirchoff 1st law

current in = current out

kirchoff 2nd law

total emf = sum of pd across components

current and pd in series

current is the same and pd is split between components

current and pd in parallel

current is split between branches and pd is the same in one loop

moles

SI base unit for the amount of a substance

kWh to Joules

multiply 3.6×10^6 and vice versa

3 ways to reduce random error

take repeated measurements, use computer or data logger, use higher resolution equipment

use of radioactive isotopes

carbon dating or medical diagnostics

evidence for discrete energy levels

line emission and absorption spectra

discrete energy levels

quantised energy states that only electrons can occupy

polarisation evidence for nature of transverse waves

can only occur if oscillations are perpendicular to direction of energy transfer

stationery wave

two waves of the same frequency and amplitude travel in opposite directions and interfere

pulse broadening

spreading out of a light pulse causes overlapping of pulses which limits the maximum data transmission rate

free vibrations

vibrations occur without external force

forced vibrations

occur due to external periodic force

line of action

straight line passing through the point where the force acts in the direction of the force vector

Core

Where light travels and has a higher refractive index

Cladding

Has a lower refractive index and allows for TIR

How to overcome material dispersion

Use monochromatic light or choose wavelengths where dispersion is minima

How to overcome modal dispersion

Single-mode fibres and graded index fibres

extra properties of stionary waves

transfers no energy and positions of max and minimum amplitude are constant

electron capture

proton becomes a neutron and electron and neutrino with W+ boson

diffraction grating equation (G) dsintheat=nlambda

G=1/d

energy for accelerating particle through a pd

E=qv

smaller wavelength leads to what (waves)

less diffraction leads to decrease in diameter

make velocity the subject qV=1/2mv² V=pd

square root 2qV/m

emf

energy supplied per unit charge by a source as it moves charge around a circuit

time taken (vertical)

t=2usintheat/g

Elastic limit

The maximum stress before permanent deformation occurs. May be beyond the limit of proportionality

Critical damping

System returns to equilibrium in the shortest possible time without oscillating

heavy(over) damping

System returns to equilibrium slowly without oscillating

distance between adjacent nodes

½ wavelength