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Higher Physics > Particles and Waves > Flashcards

Particles and Waves Flashcards

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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
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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

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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
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4
Q

magnetic pole

A
  • there are two magnetic poles: north and south
  • opposite poles attract, like poles repel
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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

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6
Q

difference between electric fields and magnetic fields

A
  • electric fields cause acceleration
  • magnetic fields cause a change in direction
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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
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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
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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
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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
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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
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12
Q

θ1

refraction

A

large angle, in air or vacuum

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13
Q

θ2

refraction

A

small angle, in denser medium

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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
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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
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16
Q

photoelectric effect

A

electrons are emitted from a metal when light of large enough frequency hits the metal

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17
Q

energy of photons

equation

A

E = hf or E = hc/λ

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18
Q

plank’s constant

h

A

6.63x10-34 Js

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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
Q

constructive interference

A
  • occurs when a peak meets peak / trough meets trough
  • path difference = mλ

where m∈W

26
Q

destructive interference

A
  • occurs when peak meets trough and cancel out to produce wave of lower or 0 amplitude
  • path difference = (m+1/2)λ
27
Q

grating equation

A

dsinθ = mλ

28
Q

producing a spectra

ways and differences

A
  • 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
Q

how are spectra produced from diffraction gratings

A
  • 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
Q

why is there a central white maximum for a white light interference pattern

A

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
Q

irradiance

I

A
  • irradiance is the power per unit area
  • I = P/A
  • measured in Wm-2
32
Q

point source

A

a point source is infinitely small and emits light equally in all directions

33
Q

irradiance and distance

A
  • irradiance is inversly proportional to the square of the distance from a point source
  • I1d12 = I2d22
34
Q

fundamental particle

A
  • the basic constituents of all matter in the universe
  • not composed of any other particles
  • they cannot be broken down any further
35
Q

leptons

A
  • electron (e)
  • electron neutrino (ve)
  • tau (τ)
  • tau neutrino (vτ)
  • muon (µ)
  • muon neutrino (vµ)
36
Q

quarks

A
  • 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
Q

hadrons

A

larger particles composed of quarks, inculding mesons and baryons

38
Q

mesons

A

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
Q

baryons

A

composed of three quarks which can be a combination of quarks and antiquarks

e.g. proton and neutron

40
Q

bosons

and corresponding fundamental force

A
  • photon - electromagnetism
  • graviton - gravity
  • gluon - strong interaction
  • W and Z bosons - weak interaction
41
Q

fundamental forces

A
  • 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
Q

what provides evidence of the neutrino?

A

beta decay

43
Q

what happens when matter and antimatter collide?

A

they annihilate leaving only energy behind

44
Q

why does the photoelectric effect provide evidence for the particle nature of light

A
  • each photon has a fixed amount of energy
  • each photon removes one electron
45
Q

features of the bohr model of the atom

A
  • positively charged nucleus
  • electrons orbiting nucleus in discrete energy levels
46
Q

why are some lines brighter on line emission spectra

A

more electrons are making those transitions per second therefore there are more photons of that frequency emitted per second

47
Q

how to verify inverse square law

A
  • obtain values for irradiance at different distances
  • plot graph of I against 1/d2
  • if straight line through the origin than law is verified

Higher Physics (4 decks)

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