Deck 28: Particle Physics

Question 1

Hadrons are thought to be

A) without structure.
B) composed of quarks.
C) composed of electrons.
D) responsible for the gravitational interaction.
E) extremely stable particles.

Answer 1

composed of quarks.

Question 2

The charge of the u quark is

A) e.
B) -1/3)e.
C) 2/3)e.
D) -2/3)e.
E) 1/3)e.

Answer 2

2/3)e.

Question 3

The charge of the particle is

A) e.
B) 1/3)e.
C) -2/3)e.
D) -e.
E) 2e.

Answer 3

-e.

Question 4

The reaction ^- ? e^- + + conserves

A) baryon numbers.
B) lepton numbers.
C) neutrino numbers.
D) particle numbers.
E) All of the above.

Question 5

The fact that the reaction ³⁷Cl + → ³⁷Ar + e^- is not observed whereas the reaction p + → n + e⁺ is observed is understandable in terms of the conservation of

A) baryon number.
B) energy.
C) lepton number.
D) charge.
E) angular momentum.

Question 6

The reaction $\mu$ ^- ? e^- + + conserves

A) muon lepton number but not electron lepton number.
B) electron lepton number but not muon lepton number.
C) neither muon lepton nor electron lepton number.
D) both muon and electron lepton numbers.
E) None of these is correct.

Question 7

A particle and its antiparticle must have

A) opposite spins.
B) opposite charges.
C) opposite masses.
D) opposite forces.
E) both opposite spins and opposite charges.

Question 8

The numbers L = +1 and B = +1 describe

A) a particle other than a lepton, a baryon, or an antibaryon.
B) a lepton and an antibaryon.
C) an antilepton and a baryon.
D) an antilepton and an antibaryon.
E) a lepton and a baryon.

Question 9

The charge of the particle is

A) e.
B) 1/3)e.
C) -2/3)e.
D) -e.
E) 2e.

Question 10

The charge of the particle is

A) e.
B) 1/3)e.
C) -2/3)e.
D) -e.
E) 2e.

Question 11

The numbers L = 0 and B = 0 describe

A) a particle other than a lepton or a baryon.
B) a lepton and an antibaryon.
C) an antilepton and a baryon.
D) an antilepton and an antibaryon.
E) a lepton and a baryon.

Question 12

The charge of the d quark is

A) e.
B) -1/3)e.
C) 2/3)e.
D) -2/3)e.
E) 1/3)e.

Question 13

Particles that participate in the weak interaction but not the strong interaction are called

A) neutrinos.
B) hadrons.
C) leptons.
D) electrons.
E) photons.

Question 14

Particles that participate in the strong nuclear interaction are called

A) neutrinos.
B) hadrons.
C) leptons.
D) electrons.
E) photons.

Question 15

The conservation law violated by the reaction p → π⁰ + e⁺ is the conservation of

A) charge.
B) energy.
C) linear momentum.
D) lepton number and baryon number.
E) angular momentum.

Question 16

The numbers L = +1 and B = -1 describe

A) a particle other than a lepton or a baryon.
B) a lepton and an antibaryon.
C) an antilepton and a baryon.
D) an antilepton and an antibaryon.
E) a lepton and a baryon.

Question 17

Leptons

A) are less massive than the lightest hadron.
B) include electrons, muons, and neutrinos.
C) participate in the weak interaction.
D) have significantly different masses.
E) All of these are correct.

Question 18

The charge of the s quark is

A) e.
B) -1/3)e.
C) 2/3)e.
D) -2/3)e.
E) 1/3)e.

Question 19

The numbers L = -1 and B = +1 describe

A) a particle other than a lepton or a baryon.
B) a lepton and an antibaryon.
C) an antilepton and a baryon.
D) an antilepton and an antibaryon.
E) a lepton and a baryon.

Question 20

An antiproton is an atomic particle that has

A) the mass of a proton and the charge of an electron.
B) the mass of an electron and the charge of a proton.
C) the mass of a neutron and the charge of a proton.
D) the mass of a proton and the charge of a neutron.
E) the mass of an electron and the charge of a positron.

Question 21

The charge of the particle dds is

A) e.
B) 1/3)e.
C) -2/3)e.
D) -e.
E) zero.

Question 22

At the present time, the truly elementary particles are thought to be the

A) quarks and leptons.
B) hadrons and baryons.
C) baryons and quarks.
D) leptons and hadrons.
E) quarks and photons.

Question 23

Current thought is that all matter is composed of

A) six quarks.
B) four quarks and four leptons.
C) six leptons.
D) six quarks and four leptons.
E) six quarks and six leptons.

Question 24

The charge of the particle with a quark composition of uss is

A) e.
B) 1/3)e.
C) -2/3)e.
D) -e.
E) zero.

Question 25

Which of the following combination of quarks represents a meson? 1) 2) 3) 4) 5) 6)

A) 1, 2, 4, 5
B) 1, 3, 5
C) 3, 6
D) 2, 4, 5
E) 2, 3, 4, 6

Question 26

The Stanford Linear Accelerator Center SLAC) can accelerate electrons to an energy of 50 GeV. The wavelength of these electrons is of the order

A) 0.2 fm.
B) 0.02 fm.
C) 0.002 fm.
D) 0.006 fm.
E) 0.008 fm.

Question 27

You want to make simultaneous measurements of the position and velocity of an electron that is moving in the positive-x direction. An alternate statement of the uncertainty principle involves relationship between position $\Delta$ x) and momentum $\Delta$ p) uncertainties in the form . If the velocity is measured to an accuracy of 10^-7 m/s, the limit of accuracy with which you can locate the electron is approximately

A) 6.6 * 10^-41 m.
B) 6.6 * 10^-27 m.
C) 4.0 m.
D) 0.58 km.
E) 4.0 mm.

Question 28

Which of the following are possible combinations of quarks?
1) 2) 3) 4) 5) 6)

A) 1, 2, 3, 5, 6
B) 1, 3, 5
C) 2, 3, 5
D) 2, 3, 4
E) 2, 3, 4, 6

Question 29

What is baryon number and electric charge in units of e) for the three-quark combination uds?

A) 1, 0
B) 1, -1
C) 1, +1
D) 1, +2
E) None of the above.

Question 30

Which of the following are possible combinations of quarks?
1) 2) 3) 4) 5) 6)

A) 1,2,3,5,6
B) 1,3,5,6
C) 2,3,5,6
D) 1,3,4,5
E) 1,3,4,5,6

Question 31

What is baryon number and electric charge in units of e) for the three-quark combination uuu?

A) 1, -2.
B) 1, -1.
C) 1, +2.
D) 1, +1.
E) None of the above.

Question 32

An alternate statement of the uncertainty principle involves relationship between position $\Delta$ x) and momentum $\Delta$ p) uncertainties in the form . Suppose that a 40-kg runner in an imaginary world in which Planck's constant has the value 100 J • s must be located at the finish line to an accuracy of ± 0.33 m to be sure that she won the race. What would be the minimal uncertainty in the speed in that world?

A) 0.12 m/s
B) 0.13 m/s
C) 0.60 m/s
D) 1.2 m/s E 15 m/s

Question 33

A possible explanation for the fact that an isolated quark has yet to be found is that

A) the force between quarks varies inversely with their separation.
B) the potential energy of the quarks decreases with their separation.
C) the force between quarks is independent of their separation.
D) the force between quarks varies inversely with the square of their separation.
E) None of these is correct.

Question 34

An alternate statement of the uncertainty principle involves relationship between position $\Delta$ x) and momentum $\Delta$ p) uncertainties in the form . An electron has a kinetic energy of 1.5 eV. If its momentum is uncertain by ± 2.5%, the minimum uncertainty in its position is approximately

A) 3.2 nm.
B) 5.0 nm.
C) 1.0 nm.
D) 2.2 nm.
E) 1.6 nm.

Question 35

The uncertainty principle states that

A) only momentum and velocity can be described with unlimited precision.
B) the displacement of a particle can be described with unlimited precision by using quantum mechanics.
C) nothing is smaller than Planck's constant.
D) the momentum and displacement cannot be measured simultaneously with unlimited accuracy.
E) either the momentum or the velocity, but not both, can be measured with unlimited accuracy.

Question 36

Which of the following combination of quarks has either zero or integral electronic charge?
1) 2) 3) 4) 5) 6)

A) 1, 2, 3, 5, 6
B) 1, 3, 5, 6
C) 2, 3, 5, 6
D) 1, 3, 4, 5
E) 1, 3, 4, 5, 6

Question 37

An alternate statement of the uncertainty principle involves relationship between position $\Delta$ x) and momentum $\Delta$ p) uncertainties in the form . A proton rest energy = 938 MeV) is confined in a space of length 3.0 *10^-15 m, about the size of a lightweight nucleus. The minimum uncertainty in its momentum is approximately

A) 2.2 * 10^-17 kg • m/s.
B) 5.5 * 10^-18 kg • m/s.
C) 3.6 * 10^-18 kg • m/s.
D) 1.8 * 10^-20 kg • m/s.
E) 8.8 * 10^-19 kg • m/s.

Question 38

Which of the following combination of quarks has either zero or integral electronic charge?
1) 2) 3) 4) 5) 6)

A) 1, 2, 3, 5, 6
B) 1, 3, 5
C) 2, 3, 5
D) 2, 3, 4
E) 2, 3, 4, 6

Question 39

Conservation laws that describe events involving the elementary particles include the conservation of

A) energy.
B) linear and angular momentum.
C) electric charge.
D) baryon and lepton numbers.
E) All of these are correct.

Question 40

An alternate statement of the uncertainty principle involves relationship between position $\Delta$ x) and momentum $\Delta$ p) uncertainties in the form . The graph shows the uncertainty in measuring the position x and momentum p of a particle in four experiments. Region 1 has area h, region 2 has area 4h, region 3 has area 2h, and region 4 has area 3h. The region that correctly represents the uncertainty principle is

A) 1.
B) 2.
C) 3.
D) 4.
E) All of these are correct.

Question 41

The field quanta associated with the strong force between quarks are called

A) photons.
B) gravitons.
C) nucleons.
D) gluons.
E) W and Z particles.

Question 42

With a microscope using photons you locate an electron in an atom to within a distance of 0.010 nm. An alternate statement of the uncertainty principle involves relationship between position $\Delta$ x) and momentum $\Delta$ p) uncertainties in the form . The uncertainty in the momentum of the electron is approximately

A) 1.1 * 10^-24 N • s.
B) 5.3 * 10^-27 N • s.
C) 5.3 *10^-24 N • s.
D) 4.2* 10^-24 N • s.
E) 1.1 * 10^-23 N • s.

Question 43

The reaction e⁺ + e^- →

A) describes the annihilation of a positron and an electron.
B) has a large probability of occurrence only if the positron is at rest or nearly at rest.
C) requires two photons moving in opposite directions to conserve linear momentum.
D) conserves the electron lepton number.
E) All of these are correct.

Question 44

The interaction that describes the forces among nucleons that hold nuclei together is

A) the strong nuclear interaction.
B) the electromagnetic interaction.
C) the weak nuclear interaction.
D) the gravitational interaction.
E) None of these is correct.

Question 45

Which of the following statements about particles and their interactions is true?

A) All particles that carry electric charge participate in the electromagnetic interaction.
B) All particles participate in gravity.
C) Some particles participate in all four interactions, whereas others participate in only some of them.
D) The strong nuclear interaction is mediated by gluons.
E) All of these are correct.

Question 46

The Starship Enterprise is powered by combining matter with antimatter. Suppose 1 kg of each are combined and ejected backward at the speed of light, what is the final speed of the Enterprise starting from rest? Assume that the mass of the Enterprise is 10,000 kg and the spaceship does not reach relativistic speed.

A) c/100
B) c/500
C) c/2000
D) c/5000
E) c/10000

Question 47

The field quanta that are thought to be mediating the gravitational force is called

A) photon.
B) graviton.
C) nucleon.
D) gluon.
E) W and Z particles.

Question 48

Virtual photons are particles that mediate the Coulomb force and travel at the speed of light. What is the approximate energy of the virtual photons that mediate between the ground state electron and the proton in a hydrogen atom? The radius of the electron in the ground state is 0.053 nm.

A) 100 eV
B) 500 eV
C) 1000 eV
D) 4 keV
E) 0.5 MeV

Question 49

Which of the following statements about antiparticles is true?

A) The charge of an antiparticle is the negative of the particle.
B) An antiparticle and particle are always created in pairs.
C) The mass of an antiparticle is the same as the particle.
D) A neutral particle is its own antiparticle.
E) All of these are correct.

Question 50

Particles that decay via the weak interaction have lifetimes of the order of

A) 10^-10 s.
B) 10^-15 s.
C) 10^-20 s.
D) 10^-23 s.
E) 10^-27 s.

Question 51

Forces between electrons or positrons and nucleons that result in beta decay are best understood in terms of

A) the strong nuclear interaction.
B) the electromagnetic interaction.
C) the weak nuclear interaction.
D) the gravitational interaction.
E) None of these is correct.

Question 52

Molecular forces and most of the everyday forces we observe among macroscopic objects are best understood in terms of

A) the strong nuclear interaction.
B) the electromagnetic interaction.
C) the weak nuclear interaction.
D) the gravitational interaction.
E) None of these is correct.

Question 53

In the present understanding of the behavior of elementary particles, the term color is used to denote

A) the wavelengths of various $\gamma$ rays emitted by the particles.
B) a property responsible for the strong forces between quarks.
C) a property that distinguishes between protons and neutrons.
D) a property that only leptons can possess.
E) nothing.

Question 54

Which of the following choices lists the four known types of forces in nature in order of decreasing strength?

A) strong nuclear, electromagnetic, weak nuclear, gravitational
B) electromagnetic, strong nuclear, weak nuclear, gravitational
C) strong nuclear, gravitational, weak nuclear, electromagnetic
D) strong nuclear, weak nuclear, electromagnetic, gravitational
E) strong nuclear, electromagnetic, gravitational, weak nuclear

Question 55

An electron with kinetic energy 589 keV collides with a positron of the same kinetic energy moving in the opposite direction. Calculate the wavelength of the two identical photons produced in the annihilation.

A) 4.22 × 10^-3 nm
B) 1.13 × 10^-3 nm
C) 2.11 × 10^-3 nm
D) 2.26 × 10^-3 nm
E) 2.26 × 10^-3 m

Question 56

The field quanta that mediate the weak nuclear force are

A) photons.
B) gravitons.
C) nucleons.
D) gluons.
E) W and Z particles.

Question 57

Particles that decay via the strong interaction have lifetimes of the order of

A) 10^-10 s.
B) 10^-15 s.
C) 10^-20 s.
D) 10^-23 s.
E) 10^-27 s.

Question 58

In quantum electrodynamics QED), the electromagnetic field is described in terms of

A) the interaction of electrons.
B) hadrons.
C) action at a distance.
D) the weak nuclear interaction.
E) the interaction of photons.

Question 59

The Coulomb force in the classical sense is understood in terms of electric fields. However, in quantum mechanics, the Coulomb force is described in terms of exchange of virtual photons between the charged particles. Why doesn't the creation of the virtual photons violate the principle of conservation of energy?

A) This is because in quantum mechanics energy is not conserved.
B) The uncertainty principle, , allows photons to be created provided they are absorbed within the time interval Δt.
C) The photons do not have any energy since they are massless.
D) The virtual photons are not real photons and hence do not carry any energy.
E) None of these is correct.

Question 60

You want to make simultaneous measurements of the position and momentum of an electron and a proton that are moving along a straight line. An alternate statement of the uncertainty principle involves relationship between position $\Delta$ x) and momentum $\Delta$ p) uncertainties in the form . If both of them are located with an uncertainty of 1 × 10^-10m, what is the ratio of uncertainty in the velocity of the electron to that of the proton?

A) 1.672
B) 1837
C) 9.109
D) 0.177
E) 5.443

Question 61

The distance to a particular galaxy is 60 million light years. If you assume Hubble's constant to be 23 km/s/10⁶ ly, then what redshift recession velocity would you expect to measure?

A) zero
B) 1.4 × 10³ km/s
C) 2.6 × 10³ km/s
D) 0.38 × 10³ km/s
E) None of these is correct.

Question 62

A classical calculation shows that the critical mass density of the universe is given by where H is the Hubble constant and G is the gravitation constant. If the density is below this value, the universe will expand forever, whereas if it is above this value the universe will eventually stop expanding and collapse. Approximately how many hydrogen atoms per m³ is the critical density equivalent to?

A) 4
B) 40
C) 400
D) 4000
E) 40,000

Question 63

Redshift measurements of a galaxy yield a recession speed of 1700 km/s. Hubble's constant H is 23-km/s/10⁶ ly. The distance to the galaxy is approximately

A) 36 × 10⁶ ly.
B) 47 × 10⁶ ly.
C) 53 × 10⁶ ly.
D) 66 × 10⁶ ly.
E) 74 × 10⁶ ly.

Question 64

In the standard model, weak charge is

A) the charge associated with the gravitational force.
B) carried by leptons and quarks.
C) carried by quarks and gluons but not leptons.
D) carried by photons.
E) a property of the W± and the Z particles.

Question 65

We think that the universe is expanding because

A) the light from distant galaxies is very faint.
B) the light from distant galaxies is very bright.
C) distant galaxies are very small.
D) the light from distant galaxies is blueshifted.
E) the light from distant galaxies is redshifted.

Question 66

There is evidence that the universe is expanding like a loaf of raisin bread baking in an oven. This means that

A) some clusters of galaxies are not getting farther away from other clusters of galaxies.
B) the expansion looks different from each cluster of galaxies.
C) the expansion looks the same from each cluster of galaxies.
D) we should be able to determine the location of the center of the expansion.
E) the universe will eventually collapse.

Question 67

Redshift measurements of a galaxy yield a recession speed of 1000 km/s. Hubble's constant H is 23-km/s/10⁶ ly. The distance to the galaxy is approximately

A) 23 × 10⁶ ly.
B) 37 × 10⁶ ly.
C) 44 × 10⁶ ly.
D) 52 × 10⁶ ly.
E) 61 × 10⁶ ly.

Question 68

In the standard model,

A) the fundamental particles are the leptons and quarks.
B) the force carriers are the photon, the W±, the Z particles, and the gluons.
C) every force in nature is due to the strong, electromagnetic, weak, or gravitational force.
D) a particle experiences one of the basic interactions if it carries a charge associated with that interaction.
E) All of these are correct.

Question 69

How far is a galaxy from Earth if it is receding from Earth at a speed of 0.1c?

A) 3.1 × 10²⁰ m
B) 1.3 × 10²² m
C) 1.3 × 10²⁵ m
D) 3.4 × 10²⁸ m
E) 1.3 × 10³⁰ m

Question 70

The scientific community now thinks that

A) the universe was formed in an explosion that took place between 10 and 15 billion years ago.
B) new matter is continuously being created in the space between the galaxies.
C) the universe is collapsing.
D) quasars originated in the nucleus of the Milky Way.
E) our Sun is at the center of the universe.

Question 71

Mesons are particles that mediate the strong nuclear force. They are thought to travel at near the speed of light and exist over a distance of $\backsim$ 1.5 fm between two nucleons in the nucleus. The mass of the mesons is of the order

A) 10 MeV/c².
B) 150 MeV/c².
C) 550 MeV/c².
D) 1000 MeV/c².
E) 3000 MeV/c².

Question 72

Assuming a radial speed of a galaxy to be 100 km/s from us and Hubble's constant to be 23 km/s/10⁶ c · y, how far is the galaxy from us?

A) 2300 ly
B) 2300 Mly
C) 4.3 Mly
D) 0.23 Mly
E) None of these is correct.

Question 73

Hubble's law can be interpreted to tell us the approximate

A) angular speed of the Milky Way.
B) temperature of our Sun.
C) force of gravity at any point in space.
D) age of the universe.
E) mass of Earth.

Question 74

Hubble's Law relates the speed of a galaxy from its distance to us. If you assume Hubble's constant to be 23 km/s/10⁶ ly, then what is the distance of a galaxy that is traveling at 10% the speed of light away from us?

A) It is not possible for a galaxy to travel so fast!
B) 1.3 × 10¹⁰ ly
C) 1.3 × 10⁹ ly
D) 1.3 × 10¹¹ ly
E) 1.3 × 10⁸ ly

Question 75

The cosmic background radiation is an important aspect of the Big Bang theory because it

A) shows that evolutionary models of the universe are incorrect.
B) does not show any redshift.
C) could not be produced in the universe as it is now, which suggests that conditions must have been different in the past.
D) discredits Hubble's law.
E) is useful in identifying the locations of important objects in the universe.

Question 76

According to Hubble's law, the age of the universe is

A) approximately 6000 years.
B) less than 6000 years.
C) roughly 1 billion years.
D) too great to estimate.
E) between 10 and 15 billion years.

Question 77

In the standard model, as with the leptons, there are 3 generations of quarks u&d, c&s, and t&b). The reason for this is

A) because a baryon contains 3 quarks.
B) because the electric charge of the quarks is +1/3 or -2/3 of e.
C) because each quark has a baryon number of 1/3.
D) all of the above.
E) something we do not yet understand.

Question 78

The property of the universe that primarily determines whether the universe will expand forever or eventually stop its expansion and contract is

A) its average abundance of heavy elements.
B) how much of its gas has been converted into stars.
C) its average temperature.
D) its total mass.
E) dependent on the amount of helium in the universe.

Question 79

The cosmic background radiation strongly suggests that

A) the energy radiated from the quasars is redshifted.
B) the universe has always been as it is today.
C) the universe evolved from a cold, rarified state.
D) the universe evolved from a hot, uniform state.
E) matter is continuously being created.