Particles and Waves Flashcards
(47 cards)
1
Q
electrical charge
forces on charged particles
A
- a physical property of matter measured in coulombs (C)
- charges can either be positive or negative
- opposite charges attract, like charges repel
2
Q
electric field
A
- a region of space around a charge where another charge will experience a force
- any charge will have an electric field around it
field lines go from positive to negative
3
Q
work done
electric fields
A
- form of energy measured in joules
- for a charged particle moving in the opposite direction to a uniform electric field it is equal to the electrical potential energy: since V = E/Q then Ew = QV
- for a particle moving in the same direction as the electric field, its equal to the kinetic energy
- if the particle is moving through a vacuum then the kinetic energy is equal to the work done so: 1/2mv2 = QV
4
Q
magnetic pole
A
- there are two magnetic poles: north and south
- opposite poles attract, like poles repel
5
Q
magnetic field
A
- a region of space around a magnet where another magnet will experience a force
- any magnet will have a magnetic field around it
field lines go from north to south
6
Q
difference between electric fields and magnetic fields
A
- electric fields cause acceleration
- magnetic fields cause a change in direction
7
Q
cathode ray tube
A
- electrons are produced by heated cathode and accelerate between plates of the anode
- the electron beam is deflected by the magnetic field produced by the deflection coils
- a tiny flash of light is produced when the electrons strike the screen
8
Q
linear accelerator
LINAC
A
- consists of hollow metal tubes placed in a vacuum
- charged particles are accelerated across the gaps between the tubes by the electric fields produced by the p.d. across the wires
- the tubes allow the A.C. to switch direction before the particle emerges - particles do not accelerate in the tubes
9
Q
cyclotron
A
- consists of two D shaped structures (‘dees’) placed in a vaccum back to back
- charged particles accelerate in a gap between the dees due to a large p.d. of high frequency A.C.
- particles change direction in the dees due to magnetic fields causing them to spin round
10
Q
synchrotron
A
- a linear accelerator that is bent into a ring
- the charged particles gain energy each time they go round
- electromagnets keep the particles travelling in a circular path
11
Q
refraction
A
- the change in velocity of a wave as it moves from one medium to another
- the wavelength and the speed of the wave will change
- the frequency will remain constant
12
Q
θ1
refraction
A
large angle, in air or vacuum
13
Q
θ2
refraction
A
small angle, in denser medium
14
Q
refractive index
n
A
- the ratio of the sin of the angle made by a wave in a vacuum to the sin of the angle of the wave in a medium (always >1)
- n = sinθ1/sinθ2
15
Q
critical angle
θc
A
- the angle of incidence such that the angle of refration is 90˚
- when angle > θc total internal reflection occurs
- when angle < θc refraction occurs
16
Q
photoelectric effect
A
electrons are emitted from a metal when light of large enough frequency hits the metal
17
Q
energy of photons
equation
A
E = hf or E = hc/λ
18
Q
plank’s constant
h
A
6.63x10-34 Js
19
Q
threshold frequency
f0
A
minimum frequency required for photoemission to occur
dependant upon the metal
20
Q
einstein’s photoelectric equation
A
hf = hf0 + 1/2meve2
energy of photon = work function + kinetic energy of photoelectron
21
Q
work function
hf0
A
minimum energy required by a photon to produce a photoelectron
22
Q
diffraction
A
the bending of waves as they pass through a gap or around the edge of an obstical
23
Q
phase relationship
A
two waves can be ‘in phase’ or ‘out of phase’
24
Q
coherent waves
A
waves which have the same frequency, speed, and wavelength, and a constant phase relationship
25
constructive interference
- occurs when a peak meets peak / trough meets trough
- path difference = mλ
| where m∈W
26
destructive interference
- occurs when peak meets trough and cancel out to produce wave of lower or 0 amplitude
- path difference = (m+1/2)λ
27
grating equation
dsinθ = mλ
28
producing a spectra
| ways and differences
- prism and diffraction grating
- in prism order of colour is red to violet; grating is violet to red
- prism has no central white maximum whereas a grating does
- one spectrum is produced by a prism whereas many spectra are produced by a grating
- spectrum produced by refraction in a prism and interference in a grating
29
how are spectra produced from diffraction gratings
- sunlight composed of continuum of frequencies of light and hence wavelengths of light
- grating provides multiple sources of light
- each wavelength will have different path difference for maxima to be produced
- short wavelelngth violet will have a smaller path difference than long wavelength red light so a spread of colours will be produced as an extended maximum
30
why is there a central white maximum for a white light interference pattern
the white light passes straight through the central gap so no colour separation occurs due to interference, as path difference is 0 for all colours
31
irradiance
| I
- irradiance is the power per unit area
- I = P/A
- measured in Wm-2
32
point source
a point source is infinitely small and emits light equally in all directions
33
irradiance and distance
- irradiance is inversly proportional to the square of the distance from a point source
- I1d12 = I2d22
34
fundamental particle
- the basic constituents of all matter in the universe
- not composed of any other particles
- they cannot be broken down any further
35
leptons
- electron (e)
- electron neutrino (ve)
- tau (τ)
- tau neutrino (vτ)
- muon (µ)
- muon neutrino (vµ)
36
quarks
- up (u) +2/3
- down (d) -1/3
- top (t) +2/3
- bottom (b) -1/3
- charm (c) +2/3
- strange (s) -1/3
37
hadrons
larger particles composed of quarks, inculding mesons and baryons
38
mesons
composed of two quarks - a quark and an anti-quark
| e.g. pion-plus (π+) is made of an up and an anti-down quark
39
baryons
composed of three quarks which can be a combination of quarks and antiquarks
| e.g. proton and neutron
40
bosons
| and corresponding fundamental force
- photon - electromagnetism
- graviton - gravity
- gluon - strong interaction
- W and Z bosons - weak interaction
41
fundamental forces
- electromagnetism - between particles whith electric or magnetic properties
- gravity - interactions between all forms of matter
- strong nuclear force - between hadrons in the nucleus
- weak interaction - between leptons, often related to radioactive decay
42
what provides evidence of the neutrino?
beta decay
43
what happens when matter and antimatter collide?
they annihilate leaving only energy behind
44
why does the photoelectric effect provide evidence for the particle nature of light
- each photon has a fixed amount of energy
- each photon removes one electron
45
features of the bohr model of the atom
- positively charged nucleus
- electrons orbiting nucleus in discrete energy levels
46
why are some lines brighter on line emission spectra
more electrons are making those transitions per second therefore there are more photons of that frequency emitted per second
47
how to verify inverse square law
- obtain values for irradiance at different distances
- plot graph of I against 1/d2
- if straight line through the origin than law is verified
