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A-Level Physics > Physics 2 - Particles and Radiation > Flashcards

Physics 2 - Particles and Radiation Flashcards

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1
Q

What are the main constituents of an atom?

A

Protons, neutrons and electrons.

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2
Q

What is meant be specific charge?

A

The charge to mass ration;
(Specific charge)=(charge)/(mass)
It has the units coulombs per kilogram (Ckg⁻¹).

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3
Q

What letter is associated with proton number?

A

𝑍.

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4
Q

What is a nucleon?

A

A constituent of the nucleus; a proton or a neutron.

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5
Q

What letter is associated with nucleon number?

A

𝐴.

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6
Q

What is the correct notation;

ᴬzX or ᶻₐX?

A

ᴬzX.

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7
Q

What is an isotope?

A

A version of an element with the same number of protons but a different number of neutrons.

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8
Q

State a use of radioactive isotopes.

A

Carbon dating; the proportion of the carbon isotope Carbon-14 in a material can be used to estimate its age.

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9
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.

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10
Q

Describe the range of the strong force.

A

It is repulsive up to 0.5fm
It is attractive between 0.5fm and 3fm
It is negligible past 3fm

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11
Q

What makes a nucleus unstable?

A

Having either too many protons, neutrons or both

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12
Q

How do nuclei with too many nucleons decay?

A

By alpha decay, where an alpha particle is emitted from the nucleus

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13
Q

What are alpha particles?

A

Helium nuclei formed of 2 protons and 2 neutrons.

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14
Q

How do nuclei with too many neutrons decay?

A

Beta minus decay, in which a neutron decays into a proton by the weak interaction (the nucleon’s quark character changes from udd to uud) and a beta minus particle is emitted (a fast moving electron).

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15
Q

How was the existence of the neutrino hypothesised?

A

The energy of particles after beta decay was lower than before, a particle with 0 charge and negligible mass must carry away this excess energy, this particle is the neutrino.

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16
Q

What is meant by beta minus decay?

A

When a neutron becomes a proton, the atom releases an electron and an anti-electron (positron) neutrino.

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17
Q

What is an antiparticle?

A

For each particle, there is an antiparticle with the same rest energy and mass, but all other properties are the opposite of its respective particle.

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18
Q

True or false; “Every particle has an antiparticle.”?

A

True.

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19
Q

What is the name of the antiparticle of an electron?

A

A positron.

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20
Q

What is the antiparticle of π0 (pion with 0 charge)?

A

Also π0, its antiparticle is itself.

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21
Q

What occurs when a particle and antiparticle meet?

A

Annihilation; the mass of the particle and antiparticle is converted back to energy in the form of 2 gamma ray photons which go in opposite directions to conserve momentum.

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22
Q

What is pair production?

A

The process in which a gamma ray photon is converted into a particle-antiparticle pair.

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23
Q

What is the minimum energy of a photon required to make a particle-antiparticle pair of a given particle?

A

Twice the particles rest energy.

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24
Q

What are the names of the four fundamental forces?

A

Gravity
The electromagnetic force
The weak nuclear force
The strong nuclear force

25
Q

What is the exchange particle of the electromagnetic force?

A

The virtual photon.

26
Q

What types of particles are affected by the strong nuclear force?

A

Hadrons.

27
Q

What is the exchange particle of the weak nuclear force?

A

The W boson (W⁺ or W⁻)

28
Q

What does the electromagnetic force act on?

A

It acts on any and all charged objects, such as when a positively charged ball repels another positively charged ball.

29
Q

When does the weak nuclear interaction occur.

A

When quark character changes (a quark changes into another quark), it affects all types of particles.

30
Q

Which properties must be conserved in particle interactions?

A 
Energy
Charge
Baryon number
Lepton number
Momentum
Strangeness (ONLY FOR STRONG INTERACTIONS)
31
Q

What is a hadron?

A

Both baryons and mesons are hadrons, hadrons are made of 2 or more quarks held together by the strong nuclear force.

32
Q

What are the classes of hadrons?

A

Baryons (which contain three quarks) and mesons (which contain one quark and one antiquark).

33
Q

The pion and kaon are both examples of which class of particle?

A

Mesons.

34
Q

The pion can be an exchange particle for which force?

A

The strong nuclear force.

35
Q

What particle does a kaon decay into?

A

A kaon decays into a pion.

36
Q

Give some examples of baryons.

A

Protons (which have the uud quark character) and neutrons (which have the udd quark character)

37
Q

What is significant about a proton?

A

It is the only stable baryon and all baryons will eventually decay into protons.

38
Q

Give some examples of leptons?

A

Electrons, muons, their neutrinos and their corresponding antiparticles.

39
Q

What does a muon decay into?

A

An electron.

40
Q

What is the strangeness value of a strange quark?

A

-1

41
Q

True or false; “Strangeness is always conserved in a weak interaction.”?

A

False, strangeness is only conserved in the strong interactions, in weak interactions it can change by 0, -1 and +1.

42
Q

Complete the sentence; “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.

43
Q

Are electromagnetic waves transverse or longitudinal?

A

Transverse.

44
Q

What phenomenon can be used to show that light behaves as a particle?

A

The photoelectric effect.

45
Q

Describe the photoelectric effect.

A

When light above a particular frequency is shone on a metal, electrons are released- these electrons are “photoelectrons”.

46
Q

What is the threshold frequency?

A

The minimum frequency of light required for an electron to be emitted.

47
Q

What equation is used to determine the energy of a photon?

A 
E=hf=hc/λ
Where:
E=Photon energy (J)
h=Planck's constant
f=Frequency (Hz)
λ=Wavelength (m)
48
Q

Why does a photon need to have a minimum frequency in order to liberate an electron?

A

The energy of a photon is determined by its frequency and the photon’s must be greater than the work function in order for an electron to be emitted.

49
Q

What is the work function?

A

The minimum energy needed to release an electron on the surface of a metal from its bonds.

50
Q

If a photon has a frequency higher than the threshold frequency, what would occur?

A

The electron will be liberated and the remaining energy is transferred to the kinetic energy of the electron

51
Q

If light is incident on a metal and photoelectric emission doesn’t occur, what is the effect of increasing light intensity?

A

Intensity=(Photon energy)(Number of photons)
By raising photon energy, the threshold frequency could be reached/passed so electrons would be emitted.
By raising the number of photons, more photons would be incident on the metal per second, but each photon still carries the same amount of energy, so no electrons are released and no effect is observed.

52
Q

What is the photoelectric equation?

A 
hf=φ+Eₖ₍ₘₐₓ₎
Where:
h=Planck's constant
f=Frequency (Hz)
φ=Work function (J)
Eₖ₍ₘₐₓ₎=Maximum possible kinetic energy of the photoelectrons (J)
53
Q

What is an electron volt?

A

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

54
Q

How do you convert between electron volts and joules?

A

Electron volt (eV)=Joules/1.6×10⁻¹⁹

55
Q

How does a fluorescent tube work?

A

High voltage is applied across mercury vapour, which accelerates fast moving, free electrons, which collide with the mercury atoms.
The mercury atoms are excited and then return to their ground state, which releases UV photons.
The tube’s phosphorus coating absorbs the UV photons, and its electrons are excited, they cascade down the energy levels and emit a range of visible light photons.

56
Q

What evidence is their for there being discreet energy levels in atoms?

A

Line emission and absorption spectra, since the lines appear at discrete points which show where a light photon of specific frequency and wavelength has been absorbed or emitted. This shows that electrons can only absorb an exact amount of energy to be excited to the next discerete energy level.

57
Q

What is wave particle duality?

A

All particles have both particle and wave properties and waves can have particle properties.

58
Q

What is the equation for de Broglie wavelength?

A 
λ=h/mv
Where:
λ=de Broglie wavelength(m)
h=Planck's constant
mv=Momentum(kgms⁻¹)

A-Level Physics (9 decks)

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