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A-level Physics Year 1 > Particles > Flashcards

Particles Flashcards

(70 cards)

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1
Q

What’s the structure of the atom ?

A
  • nucleus - positive with nucleons ( protons and neutrons)

- electrons orbit nucleus (surround)

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2
Q

Relative charge and masses of protons, neutrons and electrons ?

A 
CHARGE 
- proton = +1 
(1.60x10^-19 C)
- neutrons = 0 
- electrons = -1
(-1.60x10^-19 C)
MASS
- proton = 1 
(1.67x10^-27)
- neutron = 1 
(1.67x10^-27)
- electron = 0.0005
(9.11x10^-31)
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3
Q

How to represent elements in nuclide notation ?

A

A - nucleon number = atomic mass (p+n)
x
Z - proton number = atomic number (p)

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4
Q

What are ions ?

A

are charged atoms (lost/gained electrons)

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5
Q

How to calculate the specific charge of a particle ?

A

Charge/mass = Q/m

  • Measured in Ckg^-1
  • ignore electron mass
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6
Q

What are Isotopes ?

A

are atoms with the same number of protons and different number of neutrons

  • different masses
  • 12C6 -> 14C6
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7
Q

What’s the role of the strong nuclear force in keeping nuclei stable ?

A

it keeps the nucleus together by overcoming the electrostatic force of repulsion between the protons
- blinds nucleus + maintains its stability

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8
Q

The effect of the strong nuclear force in certain ranges ?

A

<0.5fm = repulsion
0.5fm-3fm = attraction
>3fm = no effect
- NEED TO KNOW GRAPH

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9
Q

Why do unstable particles decay ?

A

decay to make themselves more stable

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10
Q

Difference between forces ?

A 
Gravity 
- range = infinite 
- acts on = everything 
- strength = 10^-34
Electromagnetic 
- range = infinite 
- acts on = charge 
- strength = 10^-2
Weak nuclear
- range = 10^-18
- acts on = everything
- strength = 10^-5
Strong nuclear 
- range = 10^-15
- acts on = Quarks 
- strength = 1
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11
Q

Equation for ALPHA (α) decay ?

A

A -> A-4 + 4
x
Z -> Z-2 +2
e.g. helium

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12
Q

Equation for BETA - MINUS (β) decay ?

A 
A -> A + 0
x
Z -> Z+1 - 1
e.g. uranium 
- nucleus into proton
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13
Q

What are photons ?

A

are ‘wave packets’ of electromagnetic radiation

- explain photoelectric effect

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14
Q

How to calculate energy of a photon ?

A

E = hf

Photon energy = plank constant x frequency

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15
Q

What happen in Gamma Radiation (ɣ) ?

A

electromagnetic radiation emitted by unstable nucleus

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16
Q

How to convert between Joules and MeV ?

A

1eV = 1.60x10^-19J

  • MeV -> J (x1.60x10^-13)
  • J -> MeV (÷1.60x10^-13)
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17
Q

What does every particle have ?

A

has a corresponding ANTI-PARTICLE with equal rest mass but all other properties are opposite .
- same as anti-particle -> Photon (ɣ) and Pi Nought (π)

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18
Q

what happens when matter and anti-matter meet ?

A

they destroy each other and radiation is released

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19
Q

What is Pair Production ?

A

Photon -> Electron + Positron

  • only happens if enough energy to produce mass
  • access energy = more kinetic energy, greater rest mass and more pairs produced
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20
Q

How to calculate minimum energy needed for Pair Production ?

A
  • minimum energy of photon needed = hfmin = 2Eo (rest mass) - MeV
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21
Q

What is Annihilation ?

A

Electron + Positron -> Photon (ɣ) + Photon (ɣ)

  • Particle meets it’s Antiparticle
  • PET (positron) - meet with electron inside body - Annihilation
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22
Q

How to calculate minimum energy needed for a Photon produced in Annihilation ?

A
  • minimum energy of each photon produced = hfmin = Eo (rest mass) - MeV
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23
Q

What are makes Leptons ?

A

1) Do NOT experience (interact) the strong nuclear force

2) They are Fundamental

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24
Q

What particles are Leptons ?

A

Stable leptons - electrons, positrons and all their neutrinos

  • Muon (minus/plus) and muon neutrino
  • all unstable decay into -> electrons, positrons and all their neutrinos
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25
What are makes Hardrons ?
1) Do experience (interact) the strong nuclear force | 2) They are NOT Fundamental - made of Quarks
26
What particles are Hadrons ?
Stable Hadrons - protons and antiprotons | - two sections : Baryon and Mesons
27
What are Baryons ?
- Particle structure - 3 quarks or 3 antiquarks (qqq) - are conserved B ± 1 - total baryon number always conserved - unstable baryons -> protons/antiprotons and leptons
28
What are Mesons ?
- Particle structure - one quarks and one antiquarks (Qq) - are not conserved B=0 - unstable mesons -> leptons
29
what Mesons has Strangeness ?
Kaons | K+ / Ko / K-
30
Whats the quark composition of a proton, neutron ?
Proton - uud | Neutron - udd
31
When is Strangeness conserved ?
is conserved in strong interaction and not conserved in weak interaction
32
How the weak interaction can change a quark's character ?
type of quark is not conserved | - Beta Minus Decay
33
How exchange particles (virtual particles) allow forces to act between particles ?
Are particles that are transferred between two particles when a force acts between them - exist for short period but transfer energy and momentum
34
What's the exchange particles for the electromagnetic forces ?
Virtual Photons (ɣ)
35
What's the exchange particles for the weak interaction ?
Gauge Bosons | W+ or W-
36
What must be conserved in all particle reactions ?
the charge, baryon number and lepton number.
37
What are the Rules for a Feynman Diagrams ?
- time goes up - no direction of particles - exchange particle in the middle (wiggly)
38
What are the Feynman Diagram for Beta-Minus Decay ?
n -> p + e- + Ṽe | - Boson = W-
39
What are the Feynman Diagram for Beta-Plus Decay ?
p -> n + e+ + Ve | - Boson = W+
40
What are the Feynman Diagram for Electron capture ?
P + e- -> n + Ve | - Boson = W+
41
What are the Feynman Diagram for Electron-Proton collision ?
e- + P -> n + Ve | - Boson = W-
42
How Beta Minus Decay conservation of ENERGY ?
- lead to discovery of the neutrino
43
How Beta Minus Decay conservation of CHARGE ?
- neutrino has no charge - only experience weak nuclear and gravity force
44
What the Photoelectric effect ?
refers to the emission, or ejection, of electrons from the surface of, generally, a metal in response to incident light - have to use Ultra Violet because has higher frequency on Zinc plate
45
What is Threshold Frequency (fo) ?
the minimum frequency of radiation required to emit electrons from the surface - no electrons emitted below the threshold
46
What happens when you increase FREQUENCY of light ?
increase MAXIMUM KINETIC ENERGY OF EMITTED ELECTRONS
47
What happens when you increase INTENSITY of light ?
increase NUMBER OF ELECTRONS EMITTED PER SECOND
48
What to assume during the photoelectric effect ?
one photon releases one electron so photon gives up all energy tone electron - light exist as quauta
49
How to calculate the Threshold Frequency (fo) of a metal ?
``` hfo = Φ + Ek fo = Φ/h ```
50
What does Ek represent ?
the maximum kinetic energy of emitted electrons
51
How to calculate the energy of an incident photon ?
hf = Φ + Ek
52
What is the work function (Φ) of a metal ?
the minimum energy to remove an electron from the metal surface
53
What you need to change in the experiment to investigate the effect of the work function ?
the metal/material being used
54
Where do electrons exist in a atom ?
they exist in certain energy levels
55
what is meant by the ground state of an atom ?
all electrons are in the lowest possible energy levels
56
What is Excitation ?
the electron moves up from one energy level to another | - atom becomes excited
57
What is Ionisation ?
an electron is released/removed from atom | - atom becomes ionised
58
What is De-excitation ?
move to a lower energy level - release photon of exact energy - hf = E1 -E2
59
What does the smallest gap mean ?
release radiation with largest wavelength - less energy loss
60
What are the conditions for Excitation ?
the incident photon needs exact correct amount of energy to electron to absorb it and move level
61
How Fluorescent tubes work ?
- high voltage along tube accelerates electrons within low pressure gas (mercury vapour) - collision with mg and excite electrons which will emit photons - coating absorb UV photons so electrons of coating de-excite and release visible photons
62
What is stopping Potential (Vs) ?
the minimum potential needed to stop photoelectron emission | - Ek = eVs
63
What does the Vacuum Photocell graph look like ?
y = mx + c Ek = hf - Φ - double the intensity - double the photoelectrons per second = current
64
What is a Line Emission Spectrum ?
- so electrons move up from one energy level to another (excite) - electrons de-excite (fall) and release a photon - photon only have specific wavelength - intensity of line related to number of photons released
65
What experiment shows EM radiation has Particle Properties ?
Photoelectric effect
66
What experiment shows EM radiation has Wave Properties ?
Diffaction
67
What experiment shows Electrons has Particle Properties ?
Deflection in electric/magnetic fields (or photoelectric effect)
68
What experiment shows Electrons has Wave Properties ?
Diffraction
69
What is meant by Wave-particle Duality of EM radiation ?
where EM radiation behave either as a particle or as a wave | same as electrons
70
How to calculate the de Broglie wavelength a particle ?
λ = h/p = h/mv | λ∝1/p

A-level Physics Year 1 (5 decks)

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