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Physics > Particles & Radiation > Flashcards

Particles & Radiation Flashcards

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Physics 101 flashcards AP® Physics flashcards
1
Q

What is the relative mass/charge of a proton/neutron/electron

A

Charge - P = +1 / N = 0 / E = -1
Mass - P = 1 / N = 1 / E = 0.0005

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2
Q

What is alpha emission

A

When an element emits and alpha particle and loses 2 protons & 2 neutrons (4 nucleons)

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3
Q

What is beta minus emission

A

When an element has a neutron rich nucleus and a neutron decays into a proton. The reaction releases a beta - particle and an anti electron neutrino

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4
Q

What is beta plus emission

A

When an element has a proton rich nucleus and proton decays into a neutron. The reaction releases a beta + particle and an electron neutrino

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5
Q

When does alpha emission occur

A

Very big nuclei

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6
Q

How did scientists know an extra particle was released during beta emission

A

The (anti)electron neutrino carries some energy and momentum (conservation laws)

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7
Q

What are the properties of antiparticles respective to their opposite particles

A

Same mass/rest mass
Opposite charges

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8
Q

What are photons

A

Packets of EM radiation

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9
Q

What happens when you convert energy to mass

A

Equal amounts of matter & antimatter are created

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10
Q

What ray needs to be present for pair production and why

A

Gamma because its the only ray which carries that amount of energy

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11
Q

What is produced from pair production

A

Particle & anti particle pair

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12
Q

What happens in annihilation

A

A particle & anti particle pair interact and all mass converts into energy.

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13
Q

Why don’t antiparticles exist for long

A

They exist for fractions of a second before they annihilate

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14
Q

Equation for rest energy

A

Rest mass x speed of light^2

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15
Q

What is a repulsive force

A

When a force pushes two objects away from each other

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16
Q

What is an attractive force

A

When a force pushes two objects together

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17
Q

What are the 4 fundamental forces

A

Strong/weak nuclear
Gravity
EM

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18
Q

Why is gravity not used in particles

A

Force created by gravity is negligible because of mass of particle

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19
Q

What gauge bosons and particles does EM interactions have

A

Virtual photons, Affects charged particles only

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20
Q

What gauge bosons and particles does weak nuclear interactions have and what types of particles does it affect

A

W+/- bosons, Affects all types of particles

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21
Q

What gauge bosons and particles does strong nuclear interactions have

A

Pions, Only affects hadrons

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22
Q

What is the Feynman diagram of Particle repulsion

A

Two identical particles repelling off each other with a photon exchange particle

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23
Q

What is the Feynman diagram of electron capture

A

Proton + electron , W+ boson, Neutron + electron neutrino

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24
Q

What is the Feynman diagram of beta - decay

A

Neutron , W- boson , Proton + electron + anti electron neutrino

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25
Q

What is the Feynman diagram of beta + decay

A

Proton, W+ boson, Neutron + positron + electron neutrino

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26
Q

What is the Feynman diagram of electron proton collisions

A

Electron + proton , W- boson, electron neutrino + neutron

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27
Q

What is the Feynman diagram of proton-electron attraction

A

Proton + electron, photon ,Proton + electron

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28
Q

What is the Feynman diagram of Neutron neutrino interaction

A

Neutron + electron neutrino , W- boson, Proton + electron

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29
Q

What do bosons do

A

Converts Neutrons to protons vice versa
W+ positrons electron neutrinos
W- electrons anti electron neutrinos

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30
Q

What is the only stable baryon

A

Proton

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31
Q

What do all baryons decay into

A

Protons

32
Q

What happens when a neutron decays

A

Proton + electron + anti electron neutrino

33
Q

What is a lepton

A

Particle that doesn’t feel the strong nuclear force

34
Q

What is the strangeness in a strange quark

A

-1

35
Q

What can sometimes not be conserved in weak interactions

A

Strangeness

36
Q

K0 quark config

A

down, anti strange

37
Q

K+ quark config

A

up, anti strange

38
Q

K- quark config

A

strange, anti up

39
Q

K0 _ quark config

A

strange, anti down

40
Q

Pion - quark config

A

down, anti up

41
Q

Pion 0 quark config

A

down, anti down / up, anti up

42
Q

Pion + quark config

A

up, anti down

43
Q

What needs to be conserved

A

Charge, Baryon number, lepton number (both electron and muon), strangeness (only in strong)

44
Q

What are photoelectrons released with. Refer to max KE

A

Varying KE . The value for max KE increases with frequency but unaffected by intensity

45
Q

Why does the photoelectric effect not apply with wave theory

A

Energy carried is proportional to intensity
Energy carried out by light would b e spread out evenly
Each electron would gain a bit of energy for every wave until it had enough to leave the surface

46
Q

What does the photoelectric effect support

A

Einsteins photon model of light

47
Q

When are photoelectrons released

A

Frequency of the light > Threshold frequency

48
Q

When does light intensity have no effect

A

When frequency of light < Threshold frequency

49
Q

What is stopping potential

A

The potential difference needed to stop the fastest moving electrons

50
Q

Stopping potential equations

A

e x Vs = KE max
(1.6x10^-19) x stopping potential = Max KE

51
Q

Explain the graph of I against V for the photoelectric effect

A

Zero until the stopping potential then proportionally increases until it hits the saturation current then levels out

52
Q

Explain how the photoelectric effect can be seen by using a vacuum photocell

A

Power supply makes anode +ve relative to cathode, light is shone on cathode, photoelectrons attracted to anode so a complete circuit is made.
Photoelectrons are liberated from cathode and travel to anode.
Current flows
With more +ve voltage, every photoelectron that crosses = maximum current

53
Q

How does increasing light intensity affect a vacuum photocell

A

More photons a second
More photons crossing
Bigger current

54
Q

What is the equipment in a vacuum photocell

A

Anode/Cathode
Evacuated Chamber
Sensitive ammeter

55
Q

In a vacuum photocell what happens when the anode is -ve

A

Photoelectrons do work against voltage to cross gap
If electron KE>eV can electrons cross gap
If V increases eventually no electrons can cross and current = 0A (Stopping potential)

56
Q

Where are electrons in atoms

A

Discrete energy levels

57
Q

How do electrons move down energy levels

A

Emitting a photon, only having specific wavelengths

58
Q

What is n=1 state called

A

Ground

59
Q

What level is the ionisation level and what is ionisation

A

Zero, energy required to fully remove an electron from ground state

60
Q

What is de-excitation

A

High—->Low energy level coming with an emission of a photon

61
Q

What is excitation

A

Low—->High energy levels with absorption of a photon

62
Q

What happens when a high KE electron collides with an atom

A

Small chance an electron kicks out another electron leaving the ion in the next highest charge state

63
Q

What is inside a gas discharge tube

A

Two electrodes at either end
Pure sample of low pressure vapour of a substance

64
Q

How does a gas discharge tube work

A

When a high voltage is applied on the electrodes, the gas can conduct electrons.
Electrons are accelerated to high speeds towards the +ve electrode
The high energy electrons collide with vapour molecules to become excited
When vapour molecules de-excite, they emit only specific frequencies of photons

65
Q

What is absorption spectra

A

When white light passes through a cool gas and refracted off a prism, a spectra of black lines appears on a continuous spectra

66
Q

What is an emission spectra

A

When whiter light passes through an excited gas and refracted off a prism, a spectra of coloured lines appear on a black background

67
Q

What does absorption and emission spectra show

A

That each line corresponds to transitions between energy levels

68
Q

Definition of fluorescence

A

The absorption of light outside the visible spectrum and re-emitting the light in the visible spectrum

69
Q

Explain how fluorescent tube works

A

Pass a high current through the metal filament heat it
Hot enough so that electrons leave the metal surface
Thermionic emission at hot cathode generates free electrons which are accelerated towards the anode gaining KE
High energy electrons collide with mercury atoms exciting them
The mercury atoms de-excite emitting UV photons
Fluorescent coating made of phosphor atoms absorb the UV photons becoming excited
The atoms de-excite emitting visible photons

70
Q

Pros/Cons of fluorescent lights

A

P -Cheaper/Produce less waste/Much brighter
C -Lots of energy/Really hot/Mercury/Flicker

71
Q

How do waves show wave-particle duality

A

Shows light with interference and diffraction

72
Q

How do particles show wave-particle duality

A

Shows light with photoelectric effect

73
Q

What is the wave-particle theory

A

If ‘wave like’ light showed particle properties (photons), ‘particles’ like electrons should be expected to show wave-like properties

74
Q

What can the de Broglie wavelength be interpreted as

A

Probability wave

75
Q

Describe the experiment to show electron diffraction

A

An electron gun shoots electrons at an incredibly small graphite crystal
The electrons scatter in the evacuated chamber into green rings showing interference on the phosphor screen

Physics (12 decks)

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