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OCR A Physics A Level > 6.4 Nuclear > Flashcards

6.4 Nuclear Flashcards

1
Q

Alpha particle scattering experiment and what it proved

A

A stream of alpha particles were emitted at a piece of gold foil. Most of the particles went straight through, but some were reflected back. This meant that matter must be mostly empty space with small, dense positively charged pockets (the nucleus)

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2
Q

fm

A

femtometer - 10-15m

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3
Q

Standard notation for an atom

A

AZX

Where

A is mass number

Z is proton numbe

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4
Q

Strong nuclear force

A

The force that holds the nucleus together against the repulsion of the electrostatic repulsion

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5
Q

How the strong force varies with distance

A

Repulsive < 0.5 fm

Attractive enough to overcome electrostatic repulsion at < 3 fm

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6
Q

Hadron

A

Particles that feel the strong nuclear force (made of quarks)

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7
Q

What is the only stable hadron

A

Proton

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8
Q

Lepton

A

Fundamental particles that don’t feel the strong force but do feel the weak nuclear force

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9
Q

Examples of hadrons (2)

A

proton, neutron

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10
Q

Examples of leptons (2)

A

Electron, neutrino

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11
Q

Antiparticle and its properties

A

Every particle has an antiparticle with the same properties, except it will have the opposite charge

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12
Q

Pair production

A

When energy is transformed into a particle and an antiparticle

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13
Q

How a gamma ray might create antimatter

A

A high energy photon can turn into a electron and a positron via pair production. The energy of the photon (hf) is transformed into the mass of the two produced particles (leftover energy is put to their kinetic energy)

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14
Q

Annihilation

A

When a particle meets its antiparticle the mass of both is converted into energy in the form of two photons

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15
Q

Quark

A

The building block of hadrons

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16
Q

Quark composition of a proton

A

uud

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17
Q

Quark composition of a neutron

A

udd

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18
Q

up quark charge

A

+2/3

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19
Q

down quark charge

A

-1/3

20
Q

strange quark charge

A

-1/3

21
Q

β- decay

A

Occurs in a neutron rich atom. Neutron decays to a proton, electron and antineutrino. (d –> u)

22
Q

β+ decay

A

Occurs in a proton rich atom. Proton changes into a neutron and emits a positron and a neutrino, (u–>d)

23
Q

Radioactive decay

A

When a nucleus stabilises by releasing particles/energy in various forms

24
Q

Properties of radioactive decay

A

It is spontaneous and random

25
Q

What is meant by spontaneous and random

A

There is no way to know when a nucleus will decay. It can’t be predicted

26
Q

Alpha radiation

A

A helium nucleus

27
Q

β radiation

A

An electron

28
Q

γ radiation

A

A gamma ray

29
Q

ν (nu)

A

Symbol for neutrino

30
Q

Range of β+ radiation

A

Effectively 0 since it will almost instantly be annihilated by an electron

31
Q

How to investigate radioactivity

A

Place a material between a radioactive source and a geiger-muller tube and record the count rate over a period of time. Repeat with different materials

32
Q

where α emmision occurs

A

Heavy nuclei

33
Q

when γ radiation is emitted

A

When a nucleus has too much energy (often after alpha or beta decay)

34
Q

Activity

A

The number of nuclei that decay each second

35
Q

Decay constant

A

The number of nuclei that decay each second

36
Q

Equation for activity

A

decay constant * undecayed nuclei

37
Q

Half life

A

The average time taken for half of the undecayed nuclei to decay

38
Q

Experiment to determine half life of an isotope

A

Calculate the background radiation rate first using a geiger-muller counter. Fill a bottle with uraniuam salt and protactinium-234. Shake the bottle so they mix and then wait for them to seperate again. Once they have seperated take measurements by measuring the count for 10 seconds. Repeat this measurement every say 30 seconds. Plot a graph and determine half life from it

39
Q

Equations for half life, nuclei and activity

A

Just use common sense exponential maths

40
Q

How carbon dating works

A

Living things take in carbon-14 from the atmosphere and all living things will have the same ratio of carbon-12 to carbon-14. When something dies the carbon-14 decays and is not replenished so the ratio will start to decrease. Therefore how long ago something died (e.g. paper from wood) can be determined. The half life of carbon-14 is about 6000 years so it is not suitable for very long ago (e.g. dinosaurs like if u wanted to know when a stegosaurous died or something like that maybe a pterodactyl idk)

41
Q

Mass defect

A

The difference in mass between a nucleus and the sum of the masses of all its protons and neutrons if they were separated

42
Q

Binding energy

A

Equals the mass defect (E=mc2)

43
Q

Graph of binding energy per nucleon against nucleon numbner

A

Goes up steeply then peaks and slowly decreases. Peaks at Iron

44
Q

How to calculate energy released from a fission/fusion reaction

A

It is equal to the change in binding energy

45
Q

How fission reactors work

A

Rods of uranium rich in 235U undergo nuclear fission, producing energy and emitting high energy neutrons. These neutrons go on to collide with other uranium atoms causing them to undergo fission and so on, in a chain reaction. The emitted neutrons are travelling to fast to cause fission so they are slowed down by a moderator such as water. To make sure that the chain reaction remains steady and does not get out of control, control rods made of boron are lowered into the case. These absorb some of the neutrons so that there are not enough to cause the reaction to get out of control. The heat from the reaction is then used to heat water and make steam, which powers a turbine and then a generator

46
Q

Environmental impact of nuclear waste

A

Radioactive waste can take a long time to decay to safe levels

Natural distasters pose a risk to nuclear plants (e.g. Fukishima)

47
Q

How nuclear fusion reactions work

A

Light nuclei under very high temperatures (much higher than in fission) combine and form a heavier nucleus and release lots of energy

OCR A Physics A Level (10 decks)

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