Unit 5 - Nuclear Physics

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  • Created by: Phil
  • Created on: 02-04-13 16:41
Nucleon/ Mass Number.
(top) - Neutrons + Electrons.
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Atomic Number/ Proton number.
(Bottom)- Number of Protons.
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Ions.
A Charged atom. Loss or gain of electrons.
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Isotopes
Atoms with different mass ( due to diff number of Neutrons)
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Nuclides
Have an identical number of protons and neutrons.
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3 Forces in a nucleus.
Coulomb force, Gravitational force and the strong force.
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What type of force is a Coulomb force and how would you find it?
Repulsive force. Coulomb's law F = 1/4πε0 Q1Q2/r^2
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What type of force is the gravitational force and how is it found?
Attractive force. Netwon's law of gravitation F = GM1M2/r^2
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Properties of the strong force:
Attractive force but become repulsive at very short range to prevent the collapse of the nucleus. Short range. Does not depend on the charge of the nucleons. Is easily saturated by surrounding nucleons.
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Nuclear density
At
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Why are nuclei so dense?
They are tiny and only take up a fraction of the volume of the atom. The density of all nuclei are very similar due to they bening made of out the same building blocks
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Decay process of a nucleus.
1/0 n -> 1/1p + 0/-1 e + Ve (-) anti neutrino.
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What are the three quantities which must be conserved during hadron reations?
Strangeness, Baryeon number and Charge.
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Name the 6 quarks.
Up. Down, Strange, Top, Bottom, Charm.
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Charge, B number and strangeness of an Up Quark?
Q = 2/3 B= 1/3 S= 0
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Charge, B number and strangeness of an Down Quark?
Q=-1/3 B=1/3 S=0
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Charge, B number and strangeness of an Strange Quark?
Q=-1/3 B= 1/3 S= -1
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Quark comp of proton/ neutron?
P = uud N= udd
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What is responsible for Beta Decay?
The weak interaction between quarks.
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B- decay
n -> p +e+ Ve(-) [anti neutrio]
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In termso f quarks, what happens in B- decay?
A d quark changes to an U quark, an electron and an anti-neutrino
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B+ decay?
P-> n+e(+)+Ve
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What happens in terms of quarks in B+ decay?
An up quark cahnges to a down quark a positron and an nuertino.
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What does an alpha radiation particle consist of?
2 Protons and 2 neutrons (a Helium nucleus).
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What does a Beta radiation particle consist of?
An Electron.
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What does gamma radiation consist of?
An electromagnetic radiation of high frequency.
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Mass of alpha particle?
4
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Mass of electron?
1/1840 (Negligible)
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Mass of Gamma ray?
0
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Charge of an Alpha particle?
+2e
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Charge of a Beta Particle?
-1e
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Charge of a Gamma wave?
0
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Speed of alpha particle?
Slow (0.01c-0.2c)
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Speed of beta particle?
Fast >0.2c
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Speed of gamma ray?
Speed of light. C.
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What is alpha radiation absorbed by?
3-10 cm of air or 0.2mm of paper.
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What is beta radiation absorbed by?
0.3-2m of air or 1-10mm of Al
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What is gamma radiation absorbed by?
1-10 cm of lead or several m of concrete.
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What is radiation detected by?
A Geiger Múller tube.
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What does the GM tube detect?
Ionising particles that cause a current.
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How does radiation cause ionisation?
By colliding with atoms and knocking ekectrons away from them. The radiation loses it's energy in this process.
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Which radiation causes the most ionisation and why?
Alpha as it is slow and has the biggest charge. Gamma has the lowest due to it having no charge.
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What kind of process if radioactive decay?
It is spontaneous and random. Takes place with no apparent cause and is unable to predict.
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Define the decay constant and it's units.
The probability that an individual nucleus will decay in a unit time interval. Units : S^-1 or h^-1
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Define activity of a radioactive source and it's units.
Activity is the rate of nuclei decay. It's units is decays per second which is a Bq.
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How to find activity
A = Decay const * Numner of undecayed nuclei.
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Describe an activity against time graph and state what is shows.
A downward curve.Shows exponential decay.
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How to find out activity after a specific time?
A=A0 e^-λt
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How to find out the number of nuclei left after a specific time?
N = N0 e^-λt
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What is the relationship between decay const and half life?
t1/2 = ln2/λ
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How do smoke detectors work?
Alpha source causes a small ionising current between +tive and -tive. Smoke disrupts the current and is detected.
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What radioactive isotope is taken up by living organisms, and what ratio is kept constant with this isotope in living organisms?
Carbon- 14, constant ratio : carbon 14 - carbon 12.
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What happens in terms of Carbon 14 when a living organism dies?
Carbon 14 decays to produce Nitrogen, causing the ratio of carbon 14 to carbon 12 to decrease.
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How to find binding energy of a nucleus?
E=Mc^2 where m is mass defect and c is speed of light.
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How to find mass defect of a He nucleus for example?
[2(weight of nucleons)+2(weight of proton)] - Mass of He.
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Define binding energy of a nucleus/
Binding energy of a nucleus is the difference between its mass and the sum of the masses of it's neutrons and protons multiplied by the speed of light squared
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Define the binding energy per nucleon of a nucleus.
The binding energy divided by he number of nucleons in the nucleus.
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What is the element with the highest binding energy?
Iron56.
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What is the significance of elements to the right of iron56 in a binding energy per nucleon/ mass number graph?
These large elements can be split into smaller nuclei and release energy by fission.
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What is the significance of elements to the left of iron56 in a binding energy per nucleon/ mass number graph?
These elements can be fused together to form bigger elements and release energy by fusion.
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Define nuclear fission.
When a large nucleus absorbs a nucleus and splits into smaller nuclei and several neutrons
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What are thermal neutrons?
Neutrons that have lost Ke to the atoms of the moderator and have equivalent energy to typical particles at room temp.
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Material and function of Moderator?
M= Carbon or heavy water F= Slow down fast nucleons to sustain a chain reaction.
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Material and function of Coolant?
M=Co2, water, molten sodium F= Carries heat from core to steam generator.
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Material and function of Containment Vessel?
M=Concrete F= Shields the core and absorbs some of the neutrons produce in the core.
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Material and function of Fuel rods?
M=Uranium metal/oxide F= Provides fissile material.
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Material and function of Control rods?
M=Boron/Cadmium F=Absorbs neutron.
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How to find energy released by Fission?
Find the difference in binding energy between the large nucleus and the smaller nuclei.
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What is needed to cause nuclear fusion?
Very high temps to give protons a large amount of Ke to overcome the coulomb force of repulsion between them.
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What happens in terms of energy when protons approach each other?
Ke is converted to electric Pe due to coulomb force of repulsion.
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Define Fussion.
Two protons fuse together at high temperatures to release energy.
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Define Hadrons and name two types of hadrons.
Particles that feel the strong force. Baryons and Mesons.
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How many quarks make up baryons and mesons?
3 for baryons and 2 for Mesons ( an anti-quark and a quark)
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What is the Baryon number for Quarks, Leptons, Baryons and Mesons?
Baryons have a B number of 1, Quarks have a B number of 1/3. All the rest have a B number of 0.
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Name 6 Leptons.
Electron, Neutrino, Muon, Muon-neutrino, Tau, Tau-Neutrino.
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Other cards in this set

Card 2

Front

Atomic Number/ Proton number.

Back

(Bottom)- Number of Protons.

Card 3

Front

Ions.

Back

Preview of the front of card 3

Card 4

Front

Isotopes

Back

Preview of the front of card 4

Card 5

Front

Nuclides

Back

Preview of the front of card 5
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