Deck 41: Elementary Particles and the Beginning of the Universe

Question 1

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

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

Answer 1

the weak nuclear interaction.

Question 2

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

Answer 2

10^-23 s

Question 3

In the past neutrinos were thought to have zero mass.However,recent observations suggest that they have a small non-zero mass.One such observation is the electron neutrinos from the supernova 1987A which is 168,000 light-years from Earth.The neutrinos were observed within 13 seconds of each other.(Assume the supernova event occurred instantaneously.)This suggests that the difference in speed of the slowest neutrinos to the speed of light,c,is approximately

A)0.13c
B)0.87c
C)10 ⁸c
D)10 ¹¹c
E)10 ¹⁶c

Answer 3

10 ¹¹c

Question 4

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.

Question 5

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 6

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 7

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 8

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 9

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 10

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 11

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 12

Particles that have zero spin or integral spin

A)are called bosons.
B)are called fermions.
C)must be in different quantum states.
D)include protons,neutrons,and neutrinos.
E)None of these is correct.

Question 13

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 also known as the hadronic interaction.
E)All of these are correct.

Question 14

The reaction e⁺ + e^- $\to$ $\gamma$ + $\gamma$

A)describes the annihilation of a positron.
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)is an electron-positron reaction.
E)All of these are correct.

Question 15

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

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

Question 16

Spin particles

A)have spins that are integral multiples of
B)are called fermions.
C)obey the Pauli exclusion principle.
D)include protons,neutrons,and neutrinos.
E)All of these are correct.

Question 17

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 18

Particles that participate in the strong nuclear interaction are called

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

Question 19

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 20

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

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

Question 21

The charge of the particle uss is

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

Question 22

The charge of the particle dds is

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

Question 23

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 24

A conservation law that is not universal but applies only to certain kinds of interactions is conservation of

A)lepton number
B)baryon number
C)spin
D)charge
E)strangeness

Question 25

Which of the following are possible combinations of quarks?

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 26

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 $\times$ 10^-3 nm
B)1.13 $\times$ 10^-3 nm
C)2.11 $\times$ 10^-3 nm
D)2.26 $\times$ 10^-3 nm
E)2.26 $\times$ 10^-3 m

Question 27

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

Question 28

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 29

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 30

The Starship Enterprise is powered by combining matter with antimatter.Suppose 1 kg of each are combined and ejected backwards 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 31

The conservation law violated by the reaction p $\to$ $\pi$ ⁰ + e⁺ is the conservation of

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

Question 32

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 33

The reaction $\mu$ ^- $\to$ e^- + $\bar{v}_{\mathrm{e}}$ + $\bar{v}_{\mu}$ 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 34

The charge of the particle is

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

Question 35

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 36

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 37

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 38

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 39

The fact that the reaction ³⁷Cl + $\bar{v}_{\mathrm{e}}$ $\to$ ³⁷Ar + e^- is not observed whereas the reaction p + $\bar{v}_{\mathrm{e}}$ $\to$ 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 40

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 41

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

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

Question 42

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 43

The field quanta that mediate the weak nuclear force are

A)photons
B)gravitons
C)GUTs
D)gluons
E)weak vector bosons

Question 44

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 45

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

A)1,0,1
B)1,-1,1
C)1,+1,-1
D)1,+1,1
E)none of the above

Question 46

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.

Question 47

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 48

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

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

Question 49

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 50

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 between two nucleons in the nucleus $\backsim$ 1.5 fm.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 51

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 electron in the ground state and 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 52

According to the standard model,

A)the four forces of nature existed from the moment of the Big Bang.
B)energy in the form of radiation still dominates in the universe.
C)the four forces of nature were initially unified into a single force.
D)stable atomic nuclei formed in less than 0.01 s.
E)the universe was initially very cold and dense.

Question 53

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

A)photons
B)gravitons
C)GUTs
D)gluons
E)vector bosons

Question 54

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 55

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 56

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 57

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 $\Delta$ t.
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 58

Which of the following are possible combinations of quarks?

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

Question 59

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 60

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 61

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 c · y,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 $\times$ 10¹⁰ c · y
C)1.3 $\times$ 10⁹ c · y
D)1.3 $\times$ 10¹¹ c · y
E)1.3 $\times$ 10⁸ c · y

Question 62

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

A)23 $\times$ 10⁶ c·y
B)37 $\times$ 10⁶ c·y
C)44 $\times$ 10⁶ c·y
D)52 $\times$ 10⁶ c·y
E)61 $\times$ 10⁶ c·y

Question 63

A thousand years after the "Big Bang" the background temperature of the universe was at $\backsim$ 10⁵ K.The peak wavelength of the blackbody radiation at that temperature is

A)29 nm
B)290 nm
C)56 nm
D)560 nm
E)730 nm

Question 64

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 65

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

A)36 $\times$ 10⁶ c·y
B)47 $\times$ 10⁶ c·y
C)53 $\times$ 10⁶ c·y
D)66 $\times$ 10⁶ c·y
E)74 $\times$ 10⁶ c·y

Question 66

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

A)3.0 $\times$ 10²⁰ m
B)1.0 $\times$ 10²² m
C)1.2 $\times$ 10²⁵ m
D)3.0 $\times$ 10²⁸ m
E)1.0 $\times$ 10³⁰ m

Question 67

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 collapses.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 68

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

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