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Physics Unit 4 > Particle Physics > Flashcards

Particle Physics Flashcards

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1
Q

What does the proton (atomic) number tell us?

A

How many protons are in the nucleus

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2
Q

What does the nucleon number tell us?

A

How many protons and neutrons are in the nucleus

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3
Q

How can you work out how many neutrons are in the nucleus?

A

Nucleon number - proton number

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4
Q

Why must the air be removed from the alpha particle scattering experiment?

A

So the alpha particles do not collide with air molecules

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5
Q

What did Rutherford conclude from the alpha particle scattering experiment?

A

The nucleus; is charged, contains most of the mass, is very small compared to the rest of the atom

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6
Q

What is thermionic emission?

A

Electrons can be released from the surface of a metal as it is heated

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7
Q

Why is it necessary to use high energy particles in particle accelerators?

A

Because low energy particles just bounce of each other

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8
Q

How are particles accelerated in a linear accelerator?

A

The first tube has a + charge. The electrons are attracted to the first tube. When half way in the tube, the first tube becomes - and the second tube becomes +. The electrons are repelled by the first tube and are attracted the the second tube

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9
Q

Why must the tubes in a linear accelerator get longer?

A

The time spent inside the tube must be constant. Because the electrons are accelerating, their speed is increasing.

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10
Q

Why must a linear accelerator be in a vaccum?

A

So the particles do not collide with any air molecules

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11
Q

How are particles accelerated in a cyclotron?

A

2 Dees. Electric field between the Dees. Particles are accelerated in the gap between the Dees. Whilst inside the Dees the particle will move in a circular path due to a magnetic field. As acceleration increases momentum, the radius increases

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12
Q

In a cyclotron, why does the p.d need to switch direction at exactly the moment the particle exits from the dee?

A

To maintain the accelerations at exactly the correct instant

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13
Q

In the bubble chamber, what does the radius of curvature tell us?

A

The mass and charge of the particles

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14
Q

If a particle track appears from nothing, what does this tell us?

A

Particles have been created

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15
Q

When does annihilation occur?

A

When a particle and its corresponding antiparticle meet. They will disappear and be replaced by the equivalent energy

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16
Q

In any particle interaction, what 5 factors are always conserved?

A

Mass-energy, momentum, charge, lepton number, baryon number

17
Q

What is a fundamental particle?

A

Has no substructure

18
Q

What are the similarities and differences between particles and antiparticles?

A

Same mass but all other properties are opposite

19
Q

What is a baryon made up of?

A

3 quarks

20
Q

What is a meson made up of?

A

Quark and anti-quark

21
Q

Any particle which feels the strong force is called a …?

A

Hadron

22
Q

Are bayrons and mesons, hadrons?

A

Yes

23
Q

What is the conservation of mass-energy?

A

A reaction can overcome any mass difference by having the particles begin or end with more kinetic energy to make up the difference

24
Q

What does relativistic mean?

A

Particles travelling to the speed of light

25
Q

What are the characteristics of a neutrino?

A

Massless and no charge

26
Q

What is meant by ionisation?

A

Electrons have been removed/added from a molecule

27
Q

How can you deduce the charge of a particle in the bubble chamber?

A

Flemings left hand rule

28
Q

In the bubble chamber, if there is no track what can be deduced about that particle?

A

It is neutral

29
Q

What is meant by by a charge of +2/3?

A

2/3 the charge of an electron

30
Q

What is the role of a magnetic field in a cyclotron? (3)

A

The M field is perpendicular to the force/motion
Provides a centripetal force
Radius increases as speed increases ( r=p/BQ )

31
Q

What is the role of an electric field in a cyclotron? (3)

A

The E field causes the particles to accelerate across the Dees
Constant time period
P.D switches every half cycle

32
Q

Why does an electron confined within a nucleus have a very high energy? (2)

A

The de Broglie wavelength would have to be a similar size as the nucleus
The nucleus is a lot smaller than the atom

33
Q

What does relativistic mean?

A

Travelling close to the speed of light

34
Q

In a particle accelerator, why must very high energies be used?

A

To overcome the strong repulsive forces

35
Q

In a particle accelerator, how can you work out the frequency?

A

Equate E=mc^2 and E=hf

36
Q

Outline the atomic process that produces emission spectra (3)

A

Electrons gain energy to get to an energy level
Drop back down to their original energy level
Release a photon with a certain energy

Physics Unit 4 (5 decks)

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