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A2 Level - Physics > Chapter 24 - Particle Physics > Flashcards

Chapter 24 - Particle Physics Flashcards

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1
Q

Explain Rutherford’s Scattering Experiments

A

He fired alpha beams towards a thin gold metal foil in a vacuum.

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2
Q

Rutherford’s Scattering experiment- observations

A

Most of the alpha particles passed through, very few of them scattered.
1 in 10,000 were scattered for angles greater than 90 degrees.
1 in 2000 alpha particles were deflected through small angles.

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3
Q

Rutherford’s Scattering experiment- Conclusions

A
  1. Most of the atom was empty space with most of the mass concentrated at a small region- called the nucleus.
  2. The nucleus had a positive charge, because it repelled the few positive alpha particles that came near it.
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4
Q

What is the charge on any nucleus

A

+ Ze.
Where Z: atomic number of the element/
e: electronic charge.

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5
Q

Rutherford’s prediction of the size of the nucleus

A

10 ^-14

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6
Q

When an alpha particle approaches a nucleus, what is greater- kinetic energy or electrostatic forces of repulsion

A

Electrostatic forces of repulsion. Kinetic energy will be at 0, and then begin to increase as it moves away from the nucleus and accelerates.

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7
Q

When an alpha particle is fired towards a nucleus, what is the change in energy stores

A

Between electrostatic potential energy and kinetic energy.

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8
Q

Electrostatic potential Energy equation

A

Qq / 4 π ε0 d.

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9
Q

Electrostatic potential Energy equation

A

Qq / 4 π ε0 d.

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10
Q

What is d called?

A

The distance of closest approach

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11
Q

The calculation of KE = Qq / 4 π ε0 d. , gives what?

A

It gives an upper limit, as some more energetic alpha particles may get closer to the nucleus.

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12
Q

Charge of an alpha particle

A

2e

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13
Q

More energetic nucleus have

A

A radius of 10 ^-15

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14
Q

Radius of an atom

A

10^-10

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15
Q

Define au

A

1/12th the mass of a neutral carbon-12 atom.

1.661 x 10^-27 kg.

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16
Q

Calculation for the Radius of a nucleus

A

R = r0 A ^1/3

where r = 1.2 x 10^-15m

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17
Q

What is the radius of a proton

A

1.2 x 10^-15m

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18
Q

Why is the strong nuclear force needed?

A

In an atom, there are protons and neutrons.
The protons exert electrostatic forces of repulsion on the other protons. They do have the gravitational forces of attraction- but this isn’t strong enough to overcome their forces of electrostatic forces of repulsion.
So, the strong nuclear force is required to hold the entire nucleus together.
It only acts between neutron-neutron and then proton-neutrons.
It is attractive to 3fm and repulsive below about 0.5fm.

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19
Q

What is the density of nuclei

A

10^17

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20
Q

How can you prove that the density of a nuclei stays constant / regardless of the atomic number?

A

ρ = m/v .
V= volume of a sphere. where R = R = r0 A ^1/3.
and m = Au.
Then divide through, and the A’s cancel out.
All the rest of the numbers/ symbols are all constants, meaning that the density of any nucleus stays constant.

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21
Q

Define the antimatter

A

For each particle- there must be an antiparticle.
They have the same rest mass, but the opposite charge (and spin). If a particle and its corresponding antiparticle interact, then they will undergo a process called annihilate. This can mean that they destroy and release a lot of energy.

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22
Q

Antiparticle of an electron

A

Positron

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23
Q

What are the 4 fundamental forces

A

Strong nuclear
Electromagnetic
Weak nuclear
Gravitational

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24
Q

Effect of strong nuclear

A

Experienced by nucleons

25
Q

Effect of electromagnetic

A

Experienced by static and moving particles

26
Q

Effect of weak nuclear

A

Responsible for beta-decay

27
Q

Effect of gravitational

A

Experienced by all objects with mass

28
Q

Relative strength of strong nuclear

A

1

29
Q

Relative strength of electromagnetic

A

10 ^-3

30
Q

Relative strength of weak nuclear

A

10 ^-6

31
Q

Relative strength of gravitational

A

10 ^ -40

32
Q

Range of strong nuclear

A

roughly 10 ^-15.

33
Q

Range of electromagnetic

A

infinite

34
Q

Range of weak nuclear

A

roughly 10 ^-18

35
Q

Range of gravitational

A

infinite

36
Q

Define neutrino

A

A particle that’s quite similar to an electron, but has no electrical charge, and a very small mass.

37
Q

Define hadrons

A

Particles and antiparticles that are affected by the strong nuclear force.

38
Q

Define leptons

A

Particles and antiparticles that aren’t affected by the strong nuclear force.

39
Q

Examples of hadrons

A

Protons, neutrons and mesons

40
Q

Examples of leptons

A

Electrons, neutrinos and muons.

41
Q

Define a quark

A

It is one of the building blocks of all matter, and they make up protons and neutrons.

42
Q

Any particle that contains quarks is called-

A

A hadron

43
Q

What are the 3 quarks we need to know

A

up, down and strange.

44
Q

Symbol for an up quark

A

u

45
Q

Symbol for a down quark

A

d

46
Q

Symbol for a strange quark

A

c

47
Q

Charge of an up quark

A

+2/3

48
Q

Charge of a down quark

A

-1/3

49
Q

Charge of a strange quark

A

-1/3

50
Q

Define a baryon

A

Any hadrons made up with 3 quarks.

51
Q

Define a meson

A

Any hadrons made up of quarks and antiquarks.

52
Q

What are the 3 types of neutrinos

A

Electron, muon and tau.

53
Q

What is responsible for beta decay

A

The weak nuclear force

54
Q

What happens in B- decay (just description)

A

A neutron in an unstable nucleus decays into a proton, a electron and an electron antineutrino.

55
Q

What happens in B+ decay (just description)

A

A proton in an unstable nucleus decays into a neutron, a positron and an electron neutrino.

56
Q

What happens to the quarks in B- decay

A

One of the down quarks becomes an up quark.
Neutron = udd, but becomes a uud.
Total charge on both sides is -1/3e.

57
Q

What happens to the quarks in B+ decay

A

One of the up quarks becomes a down quark.
Proton = uud, but becomes a udd.
Total charge on both sides is +2/3e.

58
Q

What makes a fundamental particle

A

It can’t be broken into smaller pieces.

Ex: Neutrons and protons aren’t fundamental because they can be made up of quarks

A2 Level - Physics (11 decks)

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