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A Level Physics > Particles + Quantum > Flashcards

Particles + Quantum Flashcards

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1
Q

Nucleon definition

A

Proton or neutron inside a nucleus

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2
Q

Isotope definition

A

Same number of protons but with different number of neutrons in nucleus

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3
Q

Strong nuclear force definition

A

Force in the nucleus that overcomes the strong electrostatic repulsion of protons and neutrons, keeping them together

Attraction up to 5fm, repulsion below 1fm

Only affects hadrons

Mediated by gluons/pions

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4
Q

Specific charge equation

A

Charge/mass

Add up charges and the masses

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5
Q

Beta radiation (B-)

  • Where does it happen
  • What is emitted
A

Beta radiation consists of fast-moving electrons
Occurs in an unstable nucleus when a neutron turns into a proton
Beta particle created immediately and is emitted
ANTINEUTRINO with no charge also emitted.

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6
Q

Positron emission (B+)

  • Why does it happen
  • What is emitted
A

Takes place when a proton changes into a neutron in an unstable nucleus with too many protons.
Antiparticle of electron, carries +ve charge
NEUTRINO is emitted

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7
Q

Electron capture

A

When a proton turns into a neutron due to the interaction with an electron (WEAK INTERACTION)

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8
Q

Annihilation

A

When a particle and its antiparticle meet, they destroy each other and become radiation.

Total energy of the particle/antiparticle pair before the collision is taken away by 2 photons

Energy before = energy after
2(Rest energy) = 2hf

Minimum energy of each photon produced = rest energy of the particle/antiparticle

GAMMA RANGE OF EM SPECTRUM (large energy)

Momentum is conserved when 2 photons are emitted

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9
Q

Binding energy definition

A

Work done to separate a nucleus into its constituent neutrons and protons

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10
Q

Binding energy equation(s)

A

Binding energy = mass defect * c^2

Binding energy in MeV = mass defect in u * 931.3

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11
Q

Pair production

A

When one gamma PHOTON turns into a particle and antiparticle

Energy of photon = total energy of particle-antiparticle pair

E(photon) = 2E0 + 2(KE)

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12
Q

Mass defect definition

A

The difference in mass between the separated nucleons and the nucleus

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13
Q

Different particle groups

A

Leptons
Hadrons (quarks), including
- Baryons
- Mesons

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14
Q

Differences between leptons and hadrons

A

Leptons do NOT interact through the strong interaction
Hadrons interact through the four fundamental interactions
Hadrons: lepton number = 0

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15
Q

Differences between baryons and mesons

A

Baryons decay into protons (directly/indirectly)
Baryons have B=1, mesons have B=0
Baryons: qqq
Mesons: qq’ ( ‘ = anti)

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16
Q

Conservation rules

A

Conservation of charge:
Charge before = charge after

Conservation of energy:
Total energy of particles + antiparticles before the collision = rest energy + kinetic energy
Total energy of particles + antiparticles after the collision = rest energy + kinetic energy
Rest energy of products = total energy before - kinetic energy of products

Conservation of lepton numbers:
Total lepton number for any branch = total lepton number for that branch after the change

Baryon number before = baryon number after

17
Q

Quark combinations of:

pi+
pi-
pi

A

ud’
u’d
uu’ and dd’

18
Q

Exchange particles for interactions

A

Electromagnetic:
Photon. Range is infinite. Acts on CHARGED PARTICLES

Strong:
Gluons for INDIVIDUAL quarks, mesons for hadrons.
Range: 10^-15m. Acts on QUARKS

Weak:
w+, w-, zº (basons). range: 10^-18m. Act on QUARKS AND LEPTONS

Gravitational: graviton (undiscovered)

19
Q

Describe how the variation of the strong nuclear force with distance contributes to the
stability of the deuterium nucleus. (3 marks)

A

Short-range attraction to 3fm

Shorter-range repulsion to 0.5fm

Prevents protons and neutrons from moving closer and further apart

20
Q

Antiparticle definition

A

Particle with equal rest mass/energy

But opposite charge/baryon and lepton number

21
Q

Explain in terms of energy changes how line emission spectra are produced (3)

A

Energy levels are discrete –> emitted photon energy is discrete

Photon produced by electrons moving to lower energy levels

E = hf

Different wavelengths/frequencies are produced.

22
Q

What is the photoelectric effect?

A

The emission of photons from a metal surface

When the surface is illuminated by light of frequency greater than the threshold frequency

23
Q

Photoelectric effect observations

A

Below a certain frequency (threshold frequency) no (photo)electrons are ejected

Electrons are ejected immediately when illuminated with UV light

Intensity of EM radiation is increased, more photoelectrons are ejected

When the frequency increases, the kinetic energy of the photoelectrons increases

24
Q

Intensity and frequency - how do they adjust the result of the photoelectric effect?

A

Intensity affects number of photoelectrons emitted

Frequency of light affects the kinetic energy of the photoelectrons

25
Q

Excitation definition

A

Process when an atom absorbs energy without becoming ionised

As a result of an electron inside an atom moving from an inner shell to an outer shell

26
Q

Explain the difference between excitation and ionisation

A

In both cases, an electron receives energy

Excitation promotes an (orbital) electron to a higher energy level, allowing it to go to an outer shell (DOESN’T LEAVE ATOM)

Ionisation occurs when electron receives enough energy to LEAVE the electron

27
Q

Why is the electron configuration in an excited atom unstable?

A

Because an electron that moves to an outer shell leaves a vacancy

When this space is eventually filled, the electron emits a photon

The atom moves to a lower energy level

28
Q

Linking rest mass to rest energy

A

(Rest) Energy = (rest) mass * c^2

29
Q

Joules to (M)eV

A

Joules/1.6e-19 = eV

Joules/1.6e-13 = MeV

30
Q 
Quark combinations of:
k0
k'0
k+
k-
A

ds’
d’s
us’
u’s

31
Q

Ionisation energy definition

A

The minimum amount of energy needed to remove an electron from the ground state

A Level Physics (8 decks)

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