3.2 Particles and radiation Flashcards

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1
Q

What is ionisation?

A

The removal (or addition) of electrons from (or to) an atom or molecule

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2
Q

2 reasons why smoke detectors (that use radioactive material) are safe

A
  • Smoke detectors only emit alpha particles, which do not travel more than 4cm in air, so would be stoped before reaching outside of detector
  • Only a small quantity of material is needed
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3
Q

Unloading line on a F/e graph where plastic deformation has occurred:
- Why is the intercept non-zero?
- Why is the gradient unchanged?

A
  • Plastic deformation has caused permanent extension, hence non-zero intercept
  • Gradient unchanged because the forces between the bonds is identical before and after extension
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4
Q

3 ways to spot a weak interaction

A
  • If there is a change of quark character
  • If the interaction involves both hadrons and leptons
  • (If strangeness changes)
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5
Q

What is the work function?

A

The minimum energy an electron needs to overcome the metallic bond holding it in the metal, and be released from the surface of the metal

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6
Q

How can emission and absorption spectra be used as evidence for discrete energy levels in atoms?

A

Lines appear at discrete points which show where a light photon of specific frequency and wavelength has been absorbed (or emitted)

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7
Q

One application of annihilation?

A

PET scanners

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8
Q

Name 3 weak interactions

A

Beta plus decay
Beta minus decay
Electron capture

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9
Q

Name a source of high energy particles

A

Pions and kaons come from cosmic rays

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10
Q

Describe the role of exchange particles in the creation of forces

A

The force arises when the exchange particle moves between the other particles

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11
Q

Why is it important to test by experiment the prediction of a scientific theory?

A
  • If a reliable experiment supports a theory, the theory can be accepted, and extended on
  • If a reliable experiment does not support a theory, the theory must be changed
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12
Q

4 reason why it is necessary for many teams of scientists and engineers to collaborate in order for advancements to be made in particle physics

A
  • results of experiments must be independently peer reviewed before they are accepted
  • particle accelerators are very expensive and collaboration helps to spread the cost of building them
  • many skills and disciplines are required (which one team are unlikely to have)
  • lots of data to process (so more teams needed)
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13
Q

What is ionisation energy?

A

Energy needed to remove an electron from an atom from its ground state

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14
Q

How is an absorption spectrum created?

A
  • Passing white light through a cooled gas
  • Black lines represent the possible difference in discrete energy levels as the atoms in the gas only absorb photons of exact energies equal to exact differences
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15
Q

How is an emission spectrum created?

A
  • Passing the light emitted from a hot gas through a prism or diffraction grating
  • Coloured lines represent the possible difference in discrete energy levels as the atoms in the gas only emit photons of an exact energies equal to exact differences, as electrons move down to lower energy levels
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16
Q

What will kaons eventually decay into?

A

Pions

17
Q

What is the strong nuclear force?

A

The fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons

18
Q

State the names of the particles that are produced when a muon decays

A

electron + electron antineutrino + muon neutrino

19
Q

Name a way to detect if an electron has been released from an experiment

A

Observing tracks in a cloud chamber

20
Q

What is an isotope?

A

atoms/nuclei with same number of protons but different numbers of neutrons

21
Q

What happens when a particle and antiparticle meet?

A
  • They annihilate each other
  • Their mass is converted back into the energy of two gamma ray photons, which travel off in different directions in order to conserve momentum
22
Q

Quark composition of K0

A

down quark, strange antiquark

23
Q

Quark composition of K0bar

A

down antiquark, strange quark

24
Q

Range of strong nuclear force

A
  • repulsive up to 0.5fm
  • attractive from 0.5-3fm
  • zero past 3fm
25
Q

What are hadrons

A

Particles consisting of 2 or more quarks held together by the strong nuclear force

26
Q

What is the exchange particle for the strong nuclear force?

A

pion

27
Q

Strange particles are produced through the ___________________ and decay through the ___________________.

A

Strange particles are produced through the strong interaction and decay through the weak interaction.

28
Q

Describe the photoelectric effect

A
  • When electromagnetic radiation above a particular frequency is shone on the surface of a metal, photons transfer their energy to electrons in one-to-one interactions, and these electrons are released from the surface of the metal
  • These released electrons are called “photoelectrons”
29
Q

Define electron volt

A

The kinetic energy of an electron that has been accelerated from rest through a potential difference of 1V

30
Q

How does a fluorescent tube work?

A
  • A high voltage is applied across mercury vapour, which accelerates free electrons
  • These fast moving free electrons collide with mercury atoms, exciting and ionising them
  • When the electrons in mercury atoms fall back down to ground state, they release energy in form of a ultraviolet photon
  • Phosphor atoms in the coating of the tube absorb these UV photos and their electrons become excited to higher energy levels
  • As the de-excite, the electrons cascade down to the ground state, emitting visible light photons with a range of wavelengths
31
Q

What is wave-particle duality?

A
  • Every particle or quantum entity may be described as either a particle or as a wave
  • All particles have wave properties - all waves have particle properties
31
Q

What is wave-particle duality?

A
  • Every particle or quantum entity may be described as either a particle as wave
  • All particles have wave properties - all waves have particle properties
32
Q

Exchange particle for: 1. Electron capture 2. Electron-proton collision

A
  1. W+
  2. W-