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AQA A-level Physics > Chapter 1 - Matter and radiation > Flashcards

Chapter 1 - Matter and radiation Flashcards

1
Q

Describe model of an atom

A

Positively charged nucleus (composed of protons and neutrons) surrounded by orbiting electrons

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2
Q

What is the charge of a proton?

A

1.6x10^-19C

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3
Q

What is the charge of an electron?

A

-1.6x10^-19C
equal and opposite to charge of proton

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4
Q

What is the charge of a neutron?

A

0

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5
Q

What is the mass of a nucleon (proton and neutron)?

A

1.67x10^-27Kg

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6
Q

What is the mass of an electron?

A

9.11x10^-31Kg

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7
Q

What is the atomic number of an element?

A

Number of protons

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8
Q

What is the mass number?

A

Number of protons and neutrons

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9
Q

Write the isotopic notation

A

a - number of protons/neutrons
X
z - number of protons

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10
Q

What are isotopes?

A

Atoms of an element with the same number of protons but different number of neutrons

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11
Q

What is specific charge?

A

Charge divided by mass of particle

‘specific means ‘per unit mass’

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12
Q

What is the specific charge of a proton?

A

Charge/mass = 1.6x10^-19C/1.67x10^-27Kg = 9.58x10^7CKg^-1

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13
Q

Which subatomic particle has the largest specific charge?

A

Electron

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14
Q

Calculate the specific charge of a 2+ magnesium ion?

A

Charge/mass = 3.2x10^-19/3.98x10^-26 = 8.04 x 10^6 CKg^-1
ignore mass of electrons when calculating specific charge of ion

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15
Q

What stops a stable nuclei from disintergrating?

A

Strong nuclear force

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16
Q

What does the strong nuclear force act between?

A

Nucleons (protons and neutrons)

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17
Q

Is the strong force attractive or repulsive?

A

Both

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18
Q

Why is the strong nuclear force attractive and repulsive?

A

Attractive to keep nucleons together but also repulsive to prevent nucleus collapsing

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19
Q

When is the strong nuclear force attractive?

A

From 3-4 fm to 0.5fm

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20
Q

What are the particles emitted by a unstable nucleus called?

A

Nuclear decay

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21
Q

Name the types of radiation emitted by an unstable nucleus

A
  • Alpha radiation
  • Beta radiation
  • Gamma radiation
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22
Q

Which type of atoms feature alpha decay?

A

Very big atoms
Uranium and radium

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23
Q

What is the composition of an alpha particle?

A

2 Protons and 2 neutrons
same as a helium atom

24
Q

Write the equation for alpha decay of uranium

A

238 234 4
U -> Th + a
92 90 2

25
Q

What kind of atoms does beta minus decay occur in?

A

Neutron rich isotopes

26
Q

What happens in beta minus decay?

A

Neutron changes into a proton, a beta particle is ejected and an antineutrino is released

27
Q

Give the equation for the beta minus decay of Rhenium

A

186 187 0
Re -> Os + B + V^ e
75 76 -1

28
Q

Who discovered the neutrinos and how were they discovered?

A

Wolfgang Pauli in 1930

Energy of particles after beta decay was not the same as it was before, so neutrinos must be released to conserve energy

29
Q

What are the properties of a a neutrino?

A
  • Neutral (charge was already conserved in beta decay)
  • Zero or almost zero mass (never detected before)
30
Q

What is the equation linking wavelength, speed of light and frequency?

A

speed of light = frequency x wavelength

31
Q

What is a photon?

A

packet/ burst of electromagnetic waves

32
Q

When are electromagnetic waves/photons released from a charge particle?

A

When it loses energy

  • When a fast moving electron is stopped
  • An electron in a shell of an atom moves to a lower energy shell
33
Q

What is the equation for photon energy?

A

E = hf or E = hc/wavelength
energy (J) = planck’s constant (6.63x10^-34) x frequency (Hz)

34
Q

What is the equation for the power of a beam?

A

Power of a beam = nhf
n = number of photons in beam passing a fixed point each second

35
Q

What properties do antiparticles have compared to their corresponding particles?

A

Same mass and rest energy but with opposite charge

36
Q

What are the antiparticles of the electron, proton, neutron and neutrino?

A

electron - Positron
proton - antiproton
neutron - antineutron
neutrino - antineutrino

37
Q

What occurs in annihilation?

A

When a particle and a corresponding antiparticle meet and their mass is converted into radiation energy (photons)

Two photons produced (to conserve momentum)

38
Q

What is the equation for minimum energy of each photon produced?

A

hf(min) = Eo (rest energy of particle)

39
Q

What is pair production?

A

Photon creates a particle and corresponding antiparticle, and vanishes in the process.

40
Q

How do you calculate minimum energy of photon needed for pair production?

A

hf(min) = 2Eo

41
Q

What does PET scan stand for?

A

Positron emitting tomography

42
Q

What happens in a PET scan?

A

positron emitting isotope is administrated to the to the patient and some of it reaches the brain via the blood system. Each positron emitted travels no more than a few millimetres before it meets an electron and annihilate each other. Two gamma photons produced are detected an an image is built up from where the positron emitting nuclei are inside the brain.

43
Q

What are virtual photons?

A
  • Causes electromagnetic force between two charged objects
  • Virtual as we can’t detect them directly
  • Infinite range
44
Q

Draw the feynman diagram for electromagnetic force between 2 photons

A

Look at paper flashcards

45
Q

What is the weak nuclear force responsible for?

A

B- and B+ decay

46
Q

What happens when a neutrino interacts with a neutron?

A

Makes it change into a proton. A B- particle (electron) created and emitted

47
Q

What happens when an antineutrino interacts with a proton?

A

Makes proton change into neutron. B+ particle (positron) created and emitted as well

48
Q

What are the exchange particles of these interactions? What are their properties?

A

W bosons

  • Have non-zero rest mass (unlike photon)
  • Very short range - no more than 0.001fm
  • Positively charged (W+ boson) and negatively charged (W- boson)
49
Q

Write feynman diagrams for neutron-neutrino and proton-antineutrino interactions

A
50
Q

What is the role of W boson in beta decay?

A
  • W- boson decays into B- particle and antineutrino
  • W + boson decays into a B+particle and a neutrino
51
Q

Draw feynman diagrams for beta decay

A
52
Q

What is electron capture?

A

Proton in proton rich nucleus turns into neutron as a result of interacting through weak interaction with an inner shell electron. Also forms electron neutrino

53
Q

Draw feynman diagram for electron capture

A
54
Q

What is an electron volt? What’s its value?

A
  • Very small measurement of energy. It is the energy transferred to an electron when passing through a potential difference of 1 volt.
  • 1.6x10^-19 J
55
Q

What roles do exchange particle play in an interaction?

A

Transfers:

  • energy
  • momentum
  • force
  • charge (sometimes)
56
Q

What are antiparticles?

A

Particles that have opposite properties/quantum numbers (e.g. charge and strangeness) to a particle but has the same mass

AQA A-level Physics (31 decks)

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