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AS Level - Physics > 5th May exam > Flashcards

5th May exam Flashcards

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1
Q

Define the Big Bang

A

The creation of the Universe started at a very hot and dense singularity. Then, it expanded rapidly.

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2
Q

Define the Binding Energy

A

The minimum energy required to separate all the nucleons from the nucleus.

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3
Q

The parent nuclei is always…

A

Heavier than the daughter.
In fusion: Add up the masses of the separate parent nuclei, and it should still be greater than the mass of the daughter nuclei.

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4
Q

Define the au

A

The average distance from the Sun to the Earth

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5
Q

Define pc

A

The distance at which a radius of 1 au subtends an angle of 1 arcsecond.

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6
Q

Define intensity

A

Power per unit area.

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7
Q

What is the use of Medical tracers?

A

It is injected into the body. It is then absorbed by the body or a certain organ, and then a gamma or a beta camera is used to detect the amount of radiation coming from the tracer.

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8
Q

Define mass defect

A

The difference between the mass of the completely separated nucleons and the mass of the nucleus.

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9
Q

What is the binding energy a measure of?

A

The stability of a nucleus

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10
Q

How to identify a more stable system

A

It has a higher binding energy per nucleon.

The more energy required to break up a bond; the stronger that bond is due to stability.

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11
Q

One very important thing to note about stability in nuclear physics

A

Stability is based on the

Binding energy PER NUCLEON.

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12
Q

Define the induced fission

A

The process of bombarding stable nuclei with neutrons and making them unstable and fissionable

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13
Q

How are radioactive isotopes stored

A

Buried deep underground, in locations that are geologically stable and secure from attack.

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14
Q

Define an uncontrolled chain reaction

A

All fission neutrons produce further fission events, giving rise to energy released at an exponential rate.

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15
Q

Define Nuclear fusion

A

The process by which 2 light nuclei combine to produce a larger nucleus.

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16
Q

What happens to the BE/ nucleon in nuclear fusion

A

The binding energy per nucleon increases, the nucleons become tightly bound and it is more stable now.

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17
Q

Why can only lighter nuclei undergo fusion

A

Because their nuclei’s positive charges are a lot smaller, so you have to do less work against the electrostatic forces of repulsion to fuse them together.
By fusing them together, the mass increases, meaning that the binding energy per nucleon also increases.

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18
Q

What are the main properties of a nuclear reactor

A

A moderator, uranium, coolant, control rods.

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19
Q

Why is fusion preferred in comparison to fission?

A

The fuel for fusion is easily available.

And, fusion doesn’t produce radioactive waste.

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20
Q

Differences between nuclear fission and fusion

A
  • A nucleus is split / broken up in a fission reaction but in a fusion reaction nuclei combine.
  • High temperatures / pressures / (kinetic) energy required for fusion reaction
  • More energy per reaction produced in a fission reaction
  • A neutron causes fission reaction
  • Chain reaction possible in fission
  • ‘Larger’ nuclei produced.
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21
Q

Explain why high temperatures and pressures are required for fusion

A
  • There is repulsion between the nuclei.
  • At high temperatures, the particles have more kinetic energy, so a greater chance of fusion.
  • At high temperatures, the nuclei get close enough to experience the attractive nature of the strong nuclear force.
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22
Q

Why does the transmitted intensity of the X-Ray decrease when it passes through matter?

A

Intensity decreases in the original direction because the photon are scattered.

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23
Q

Fundamental particles

A

Leptons are fundamental particles, but hadrons aren’t.

Hadrons are made up of quarks.

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24
Q

What are fundamental particles

A

Leptons and quarks.

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25
Q

Types of hadrons

A

Baryons: made up of 3 quarks
Mesons: made up of 2 quarks.

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26
Q

What is a meson

A

A hadron which is made up of 2 quarks, a quark and an antiquark.

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27
Q

What is a Kaon

A

A type of meson.

There are 3 types, K^+, K^- and K^0.

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28
Q

What is a pion

A

A type of meson as well.

There are 3 types, π^+, π^- and π^0.

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29
Q

What is bigger, Kaon or pion?

A

Kaon is bigger, it decays into the pion.

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30
Q

Define a baryon

A

Protons or hadrons that decay into protons.

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31
Q

Define a meson

A

Hadrons that don’t decay into protons.

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32
Q

Describe the evolution of the Universe up until the formation of the first nuclei

A

At the Big Bang, the Universe is a singularity, and very dense and hot.
It suddenly expanded, producing high energy gamma photons.
Quarks and leptons form.
The quarks combine to form hadrons.
The neutrons and protons combine to make nuclei.

33
Q

State and explain why patients aren’t allowed to have full body CT Scans too often

A

It takes quite a long time to do.

And the patients are exposed to large amounts of ionising radiation that could cause cancer.

34
Q

Important points for how a CT Scan is made

A

Idea that more X-Ray is absorbed by the more dense materials such as the bone.
The X-Rays are attenuated by the photoelectric effect and a contrast medium may be used.

35
Q

Explain how an ultrasound is produced using the piezoelectric effect using a crystal such as a quartz.

A

You apply an ALTERNATING PD at its resonant frequency across the ends of the quartz no they stretch and compares repeatedly to produce ultrasound.

36
Q

Explain PET Scans

A

There is a ring of detectors around the body.
The positrons annihilate when they interact with electrons, producing 2 identical gamma photons travelling in opposite direction.
The delay time in the photons is used to determine the location of the annihilation. The computer is connected to the detectors and an image is formed by the computer.

37
Q

2 main properties of ultrasound

A

It is a longitudinal wave and has a frequency greater than 20kHz

38
Q

Define a radioisotope

A

A material with nuclei which are unstable and will decay

39
Q

When finding the Z2 for acoustic impedance, think whether the Z2 should be bigger than the Z1 etc.

A

Often the Z2 is smaller than the Z1. So, think about that, and depending on that, think whether you should take the positive or the negative root

40
Q

Describe and explain the evolution of a star much more massive than our Star

A

The hydrogen runs out, the outer layers of the star expands, forming a super red giant.
The core of the star collapses, and a supernova is formed.
Depending on the initial mass of the star, a neutron star or a black hole is formed.

41
Q

Where does Hubble’s law apply?

A

It only applies to galaxies, and not stars.

42
Q

Describe the evolution of the Universe from the separation of the four fundamental forces
to the formation of atoms.

A

At the beginning, the Universe was a very hot and dense singularity, and then it started to expand rapidly. The creation of matter began here, creating more matter than antimatter. First, quarks and leptons were made, and then the quarks combined to form hadrons. The hadrons also eventually joined together to form nuclei, and eventually, they became atoms.

43
Q

Describe how the absorption spectrum of a star further away would look in comparison to one that’s closer.

A

That galaxy would experience greater red shift, so it would have a longer wavelength since it’s also moving faster.

44
Q

Suggest why hydrogen spectral lines might often be used to measure a star’s velocity

A

Hydrogen is most common element in stars or Hydrogen has most intense (spectral) lines.
Intensity of light from other elements may be too low for accurate measurement.

45
Q

State and explain how stellar parallax is used to measure distances in space

A

Apparent motion or displacement of a star relative to the position of more distant stars.
Caused by the Earth’s orbit around the Sun.
An angle of parallax of 1 arcsecond when displacement
of Earth is 1AU corresponds to distance 1 pc

46
Q

Why is carbon dating unreliable if the sample isn’t too old?

A

There is a small change in the radioactivity.

47
Q

Why is carbon dating unreliable if the sample is too old?

A

Then there is very little amount of C-14 atoms, and so the activity would be too small.

48
Q

What is a decay constant

A

Probability of decay per unit time.

49
Q

What is background radiation?

A

Radiation that is always present.

50
Q

Source of background radiation?

A

Cosmic rays, space, Sun

51
Q

What is the N in A= lambda N

A

The number of nuclei

52
Q

What stops alpha radiation?

A

A sheet of paper

53
Q

What stops beta radiation?

A

Aluminium

54
Q

What stops gamma radiation?

A

Lead or concrete

55
Q

What is a muon?

A

A lepton.
It has the same charge as an electron, but it has 200 times the mass, so it’s a fat electron basically.
There are 2 types, the positively charged one, and negatively charged one.

56
Q

What forces are felt by all hadrons

A

The strong nuclear force, weak nuclear force and gravitational force

57
Q

Timeline of the Universe:

What happened at The Big Bang?

A

Time and space is creates, the universe is a singularity and it is infinitely dense and hot.

58
Q

Timeline of the Universe: 10 ^-35s

A

The Universe expands rapidly, and there is no matter created, just high energy gamma photons.

59
Q

Timeline of the Universe: 10^-6s

A

The first fundamental particles (quarks and leptons) are created.

60
Q

Timeline of the Universe: 10^-3

A

The quarks combine to form the first hadrons, such as protons and neutrons.

61
Q

Timeline of the Universe: 1s

A

The creation of matter stops after about 1s.

62
Q

Timeline of the Universe: 100s

A

Protons and neutrons fuse together to form deuuterium and helium nuclei.

63
Q

Timeline of the Universe: 380,000 years

A

The Universe cools enough for the first atoms to form.

64
Q

Timeline of the Universe: 30 million years

A

The first stars appear, and through nuclear fusion in these stars, the heavier elements begin to form.

65
Q

Timeline of the Universe: 200 million years

A

Our galaxy forms.

66
Q

Timeline of the Universe: 9 billion years

A

The Solar System forms from the nebula left by the supernova of a larger star.

67
Q

How are emission spectral lines created?

A

They are created when a p.d is applied across a hot gas, which causes the electrons in the atoms to be excited to higher energy levels. Then, when they de-excite, the produce photons which are given out.
This produces coloured lines on a black background.

68
Q

What produces a continuous spectrum?

A

Black bodies- except that they don’t exist.

69
Q

What produces an absorption spectrum?

A

When stars give out EM radiation, the compounds in the atmosphere of that star will absorb certain wavelengths of light, and this creates the black lines on a coloured background.

70
Q

How can you calculate the age of an object by knowing its activity based on C-14?

A

Calculate the decay constant (in years, or whatever unit it is asked for in).
Then, they should give you the activity of the same object that is alive. So use this as your value for A0, and the activity of the dead object as your A.
Then calculate t using the exponential equation.

71
Q

X- Rays calculations note

A

If they ever ask to calculate the minimum photon wavelength produced, then you have to use all the kinetic energy = photon energy.

72
Q

Medical Imaging- what does the N=N0 e etc. equation show you?

A

The amount of radiation that is being transmitted!!!

73
Q

Why are alpha and beta emissions known as ionising?

A

Because they can collide into atoms, and remove electrons from the atoms, leading to a charged ion.

74
Q

Why do beta particles have a greater range than alpha particles?

A

Because they have less mass, charge and are smaller, so they lose their energy over a larger distance.

75
Q

Why may the count rate on a GM tube be lower than the actual radioactivity

A

Because not all radiation will go towards the GM tube, and instead go to another direction. Some particles may actually be absorbed by the window.

76
Q

Why is beta radiation something to not care about (in comparison to gamma)

A

Because it has a short range, and it ionises quickly, so it’ll lose its energy ionising the air particles.

77
Q

Explain the shape of the binding energy per nucleon to nucleon number graph.

A

Actual graph: It peaks at iron- which is mass 56, and BE/nucleon of 8.8MeV.
The greater the binding energy, the greater the stability of the elements, and nucleons always react to become more stable. This causes a reduction n the mass, so that energy can be released, due to the equation, E=MC^2.
For fusion, the smaller nuclei combine to form a nucleus of larger binding energy per nucleon, so that stability increase.
For fission, the larger nucleon numbers split so that smaller nucleons of smaller nucleon number are formed, which again increases the stability, and releases energy.

Also, as the gradient of the curve is large in fusion than in fission, this means that there is greater energy per nucleon released for fusion than for fission.

78
Q

What quarks do all Kaons have?

A

Strange.

79
Q

What particle is produced when a particle and its antiparticle annihilate?

A

the 0 pion

AS Level - Physics (15 decks)

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