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Physic
Q:
Two billion years ago, a natural nuclear reactor formed in a uranium deposit in Africa. Why is it not possible for such a natural reactor to form somewhere on Earth today?
A) It is in fact possible for this to occur.
B) Too much uranium has already been mined for this to occur.
C) Too much 235U has now decayed for a critical mass to form naturally.
D) The remaining uranium deposits are too far underground for this to occur.
E) Uranium in the remaining deposits is mixed with too many other elements for this to occur.
Q:
What was the most convincing evidence that a natural nuclear reactor formed two billion years ago in a uranium deposit in Africa?
A) the relative depletion of 235U in the deposit
B) the relative depletion of 238U in the deposit
C) the relative abundance of lead in the deposit
D) the isotopic distribution of neodymium in the deposit
E) the appearance of radiation damage in the surrounding rock
Q:
In a neutron-induced fission process, delayed neutrons come from:
A) the fission products
B) the original nucleus just before it absorbs the neutron
C) the original nucleus just after it absorbs the neutron
D) the moderator material
E) the control rods
Q:
The purpose of a moderator in a nuclear reactor is to:
A) provide neutrons for the fission process
B) slow down fast neutrons to increase the probability of capture by uranium
C) absorb dangerous gamma radiation
D) shield the reactor operator from dangerous radiation
E) none of the above
Q:
The function of the control rods in a nuclear reactor is to:
A) increase fission by slowing down the neutrons
B) decrease the energy of the neutrons without absorbing them
C) increase the ability of the neutrons to cause fission
D) decrease fission by absorbing neutrons
E) provide the critical mass for the fission reaction
Q:
If a control rod is pulled rapidly out of a nuclear reactor core, what controls the response time (how fast the power level increases)?
A) the speed at which the rod can be removed
B) the speed at which neutrons are captured
C) the rate at which delayed neutrons from beta decay of fission fragments are emitted
D) the rate at which the coolant circulates in the core
E) the time between when a neutron is captured and when the nucleus actually fissions
Q:
In the normal operation of a nuclear reactor:
A) control rods are adjusted so the reactor is subcritical
B) control rods are adjusted so the reactor is critical
C) the moderating fluid is drained
D) the moderating fluid is continually recycled
E) none of the above
Q:
In a subcritical nuclear reactor:
A) the number of fission events per unit time decreases with time
B) the number of fission events per unit time increases with time
C) each fusion event produces fewer neutrons than when the reactor is critical
D) each fusion event produces more neutrons than when the reactor is critical
E) none of the above
Q:
A nuclear reactor is operating at a certain power level, with its multiplication factor adjusted to unity. The control rods are now used to reduce the power output to one-half its former value. After the reduction in power the multiplication factor is maintained at:
A) 1/4
B) 1/2
C) 1
D) 2
E) 4
Q:
In a nuclear reactor the fissionable fuel is formed into pellets rather than finely ground and mixed with the moderator. This reduces the probability of:
A) non-fissioning absorption of neutrons
B) loss of neutrons through the reactor container
C) absorption of two neutrons by single fissionable nucleus
D) loss of neutrons in the control rods
E) none of the above
Q:
An explosion does not result from a small piece of 235U because:
A) it does not fission
B) the neutrons released move too fast
C) 238U is required
D) too many neutrons escape, preventing a chain reaction from starting
E) a few neutrons must be injected to start the chain reaction
Q:
In a nuclear power plant, the power discharged to the environment:
A) can be made zero by proper design
B) must be less than the electrical power generated
C) must be greater than the electrical power generated
D) can be entirely recycled to produce an equal amount of electrical power
E) is none of the above
Q:
Which one of the following is NOT needed in a nuclear fission reactor?
A) Moderator
B) Fuel
C) Coolant
D) Control device
E) Accelerator
Q:
Separation of the isotopes of uranium requires a physical, rather than chemical, method because:
A) mixing other chemicals with uranium is too dangerous
B) the isotopes are chemically the same
C) the isotopes have exactly the same number of neutrons per nucleus
D) natural uranium contains only 0.7% 235U
E) uranium is the heaviest element in nature
Q:
The approximate amount of energy emitted in the fission of a nucleus such as 235U is:
A) 200 eV
B) 7.6 MeV
C) 200 MeV
D) 760 MeV
E) 200 GeV
Q:
235U is readily made fissionable by a thermal neutron but 238U is not because:
A) the neutron has a smaller binding energy in 236U
B) the neutron has a smaller excitation energy in 236U
C) the potential barrier for the fragments is less in 239U
D) the neutron binding energy is greater than the barrier height for236U and less than the barrier height for 239U
E) the neutron binding energy is less than the barrier height for 236U and greater than the barrier height for 239U
Q:
Which one of the following represents a fission reaction that can be activated by slow neutrons?
Q:
The barrier to fission comes about because the fragments:
A) attract each other via the strong nuclear force
B) repel each other electrically
C) produce magnetic fields
D) have large masses
E) attract electrons electrically
Q:
When uranium undergoes fission as a result of neutron bombardment, the energy released is due to:
A) oxidation of the uranium
B) kinetic energy of the bombarding neutrons
C) radioactivity of the uranium nucleus
D) radioactivity of the fission products
E) a reduction in binding energy
Q:
The binding energy per nucleon:
A) increases for all fission events
B) increases for some, but not all, fusion events
C) decreases for all fusion events
D) decreases for some, but not all, fission events
E) remains the same for all fusion events
Q:
The table lists properties of several heavy nuclei when they are struck by thermal neutrons; Enis the excitation energy and Ebis the energy barrier. Which quantity, or combination of quantities, represents the energy put into the oscillation of the resulting compound nucleus?A) EnB) EbC) En- EbD) Eb- EnE) Mass of the target nuclide + Eb
Q:
The energy supplied by a thermal neutron in a fission event is essentially its:
A) excitation energy
B) binding energy
C) kinetic energy
D) rest energy
E) electric potential energy
Q:
When fissions, the products might be:
A) , , and a proton
B) , , and a neutron
C) and D) , , and an alpha particle
E) two uranium nuclei
Q:
When 236U fissions the fragments are:
A) always 140Xe and94Sr
B) always identical
C) never 140Xe and 94Sr
D) never identical
E) none of the above
Q:
If the nucleus of a lead atom were broken into two identical nuclei, the total mass of the result would be:
A) the same as before
B) greater than before
C) less than before
D) converted into radiation
E) converted into kinetic energy
Q:
Consider the following energies:
1_ minimum energy needed to excite a hydrogen atom
2_ energy needed to ionize a hydrogen atom
3_ energy released in 235U fission
4_ energy needed to remove a neutron from a 12C nucleus
Rank them in order of increasing value.
A) 1, 2, 3, 4
B) 3, 4, 2, 1
C) 1, 2, 4, 3
D) 2, 1, 4, 3
E) 2, 4, 1, 3
Q:
In the uranium disintegration series:A) the emission of a particle increases the mass number Aby one and decreases the atomic number Zby oneB) the disintegrating element merely ejects atomic electronsC) the emission of an particle decreases the mass number Aby four and decreases the atomic number Zby twoD) the nucleus always remains unaffectedE) the series of disintegrations continues until an element having eight outermost orbital electrons is obtained
Q:
Consider all possible fission events. Which of the following statements is true?
A) Light initial fragments have more protons than neutrons and heavy initial fragments have fewer protons than neutrons
B) Heavy initial fragments have more protons than neutrons and light initial fragments have fewer protons than neutrons
C) All initial fragments have more protons than neutrons
D) All initial fragments have about the same number of protons and neutrons
E) All initial fragments have more neutrons than protons
Q:
Fission fragments usually decay by emitting:
A) alpha particles
B) electrons and neutrinos
C) positrons and neutrinos
D) only neutrons
E) only electrons
Q:
Magic nucleon numbers are associated with:
A) nuclei that decay via alpha decay
B) nuclei that decay via beta decay
C) nuclei that have equal numbers of protons and neutrons
D) nuclei that are relatively stable
E) nuclei that fission readily
Q:
The model of the nucleus in which each nucleon has its own well-defined quantum numbers is called the:
A) collective model
B) quantum model
C) liquid drop model
D) independent model
E) atomic model
Q:
A typical mammogram X-ray results in a radiation dose equivalent of 70 mrem. What absorbed dose does this correspond to?
A) 70 mGy
B) 70 Sv
C) 7.0Gy
D) 0.70Sv
E) 0.70 Gy
Q:
The sievert is the correct unit to use in reporting the measurement of:
A) the rate of decay of a radioactive source
B) the ability of a beam of gamma ray photons to produce ions in a target
C) the energy delivered by radiation to a target
D) the biological effect of radiation
E) none of the above
Q:
The gray is the correct unit to use in reporting the measurement of:
A) the rate of decay of a radioactive source
B) the ability of a beam of gamma ray photons to produce ions in a target
C) the energy delivered by radiation to a target
D) the biological effect of radiation
E) none of the above
Q:
The becquerel is the correct unit to use in reporting the measurement of:
A) the rate of decay of a radioactive source
B) the ability of a beam of gamma ray photons to produce ions in a target
C) the energy delivered by radiation to a target
D) the biological effect of radiation
E) none of the above
Q:
A fly caught in amber is thought to be 3 million years old. Why would it not be useful to confirm its age using radiocarbon dating?
A) The fly contains no carbon.
B) The fly is too small to contain a measurable amount of carbon.
C) The fly is too old to contain a measureable amount of carbon-14.
D) The carbon-14 doesn"t begin to decay until the fly is removed from the amber.
E) Radiocarbon dating is too inaccurate to be useful.
Q:
40K decays to 40Ar with a half-life of 1.25 x 109yr. Assume that rocks contain no 40Ar when they form, and that the only way 40Ar can be present is through the decay of 40K. If the ratio of 40K to 40Ar in a particular rock is found to be 1:3, what is the age of the rock?
A) 1.25 x 109yr
B) 2.50 x 109yr
C) 3.75 x 109yr
D) 5.00 x 109yr
E) cannot be determined without knowing how much 40K was in the rock to begin with
Q:
A certain nucleus, after absorbing a neutron, emits a and then splits into two alpha particles. The (A, Z) of the original nucleus must have been:A) 6, 2B) 6, 3C) 7, 2D) 7, 3E) 8, 4
Q:
The 66Cu (Z= 29) produced in a nuclear bombardment is unstable, changing to 66Zn (Z= 30) by the emission of:
A) a proton
B) a gamma ray photon
C) a positron
D) an electron
E) an alpha particle
Q:
An atom of 235U (Z= 92) disintegrates to 207Pb (Z= 82) with a half-life of about a billion years by emitting seven alpha particles and ______ particles:A) 3B) 4C) 5D) 6E) 7
Q:
A nucleus with mass number Aand atomic number Zundergoes ï¢ï€ +decay. The mass number and atomic number, respectively, of the daughter nucleus are:
A) A" 1, Z" 1
B) A" 1, Z+ 1
C) A+ 1, Z" 1
D) A, Z+ 1
E) A, Z" 1
Q:
A nucleus with mass number Aand atomic number Zundergoes decay. The mass number and atomic number, respectively, of the daughter nucleus are:A) A, Z- 1B) A-1, ZC) A+ 1, Z- 1D) A, Z+ 1E) A, Z- 1
Q:
A radioactive atom X emits a particle. The resulting atom:A) must be very reactive chemicallyB) has an atomic number that is one more than that of XC) has a mass number that is one less than that of XD) has an atomic number that is one less than that of XE) is the same chemical element as X
Q:
The energies of electrons emitted in decays have a continuous spectrum because:A) the original neutron has a continuous spectrumB) the neutrino can carry off energyC) the emitted electron is freeD) energy is not conservedE) the daughter nucleus may have any energy
Q:
In addition to the daughter nucleus and an electron or positron, the products of a beta decay include:
A) a neutron
B) a neutrino
C) a proton
D) an alpha particle
E) no other particle
Q:
Beta particles from various radioactive sources all have:
A) the same mass
B) the same speed
C) the same charge
D) the same deflection
E) the same energy in a magnetic field
Q:
A beta particle is:
A) a helium nucleus
B) an electron or a positron
C) a radioactive element
D) any negative particle
E) a hydrogen atom
Q:
Some alpha emitters have longer half-lives than others because:
A) their alpha particles have greater mass
B) their alpha particles have less mass
C) their barriers to decay are higher and wider
D) their barriers to decay are lower and narrower
E) their decays include the emission of a photon
Q:
A radium atom, 226Ra (Z= 86), emits an alpha particle. The number of protons in the resulting atom is:
A) 84
B) 85
C) 86
D) 88
E) some other number
Q:
Radioactive polonium, 214Po (Z= 84), decays by alpha emission to:
A) 214Po (Z= 84)
B) 210Pb (Z= 82)
C) 214At (Z= 85)
D) 218Po (Z= 84)
E) 210Bi (Z= 83)
Q:
A nucleus with mass number Aand atomic number Zemits an alpha particle. The mass number and atomic number, respectively, of the daughter nucleus are:A) A, Z-2B) A- 2, Z- 2C) A- 2, ZD) A- 4, ZE) A- 4, Z- 2
Q:
Rank the following collections of particles according to the total binding energy of all the particles in each collection, least to greatest. collection 1: 244Pu (Z = 94) nucleus alone collection 2: 240U (Z = 92) nucleus, particle collection 3: 240U (Z = 92) nucleus, two separated protons, two separated neutronsA) 1,2,3B) 3,2,1C) 2,1,3D) 1,3,2E) 2,3,1
Q:
An alpha particle is:
A) a helium atom with two electrons removed
B) an aggregate of two or more electrons
C) a hydrogen atom
D) the ultimate unit of positive charge
E) sometimes negatively charged
Q:
Bombardment of 28Si (Z= 14) with alpha particles may produce:
A) a proton and 31P (Z= 15)
B) hydrogen and 32S (Z= 16)
C) a deuteron and 27Al (Z= 13)
D) helium and 31P (Z= 15)
E) 35Cl (Z= 17)
Q:
Aluminum has atomic number 13, helium has atomic number 2, and silicon has atomic number 14. In the nuclear reaction 27Al + 4He->30Si + ( ) the missing particle is:A) anparticleB) a positronC) an electronD) a protonE) a neutron
Q:
Magnesium has atomic number 12, hydrogen has atomic number 1, and helium has atomic number 2. In the nuclear reaction 24Mg + 2H ï‚®( ) + 4He the missing quantity is:
A) 23Na (Z= 11)
B) 22Ne (Z= 10)
C) 21Na (Z= 11)
D) 21Ne (Z= 10)
E) 22Na (Z= 11)
Q:
In an alpha decay the disintegration energy appears as:
A) photon energies
B) the kinetic energies of the alpha and the daughter nucleus
C) the excitation energy of the daughter nucleus
D) the excitation energy of the alpha particle
E) heat
Q:
The relation between the disintegration constant and the half-life T of a radioactive substance is:A) = 2TB) = 1/TC) = 2/TD) T = ln 2E) T = ln(1/2)
Q:
The half-life of a radioactive substance is:
A) half the time it takes for the entire substance to decay
B) usually about 50 years
C) the time for radium to change into lead
D) calculated from E= mc2
E) the time for half the substance to decay
Q:
One curie is equivalent to:
A) one Becquerel
B) one decay per second
C) 3.0 x 108decays per second
D) 3.7 x 1010decays per second
E) 106Becquerel
Q:
The relationship between the activity R, the disintegration constant , and the remaining number Nof radioactive nuclei is:
Q:
The graph shows the decay rateRas a function of the time tfor three radioactive samples. Rank the samples according to their half-lives, shortest to longest. A) 1, 2 ,3
B) 1, 3, 2
C) 2, 1, 3
D) 2, 3, 1
E) 3, 1, 2
Q:
The half-life of a radioactive isotope is 140 days. In how many days does the decay rate of a sample of this isotope decrease to one fourth its initial decay rate?
A) 35 days
B) 70 days
C) 105 days
D) 210 days
E) 280 days
Q:
At the end of 14 min, 1/16 of a sample of radioactive polonium remains. The corresponding half-life is:
A) (7/8) min
B) (8/7) min
C) (7/4) min
D) (7/2) min
E) (14/3) min
Q:
The half-life of a radioactive isotope is 6.5 h. If there are initially 48 x1032atoms of this isotope, the number of atoms of this isotope remaining after 26 h is:A) 12 x1032B) 6 x1032C) 3 x1032D) 6 x104E) 3 x102
Q:
210Bi (an isotope of bismuth) has a half-life of 5.0 days. The time for three-quarters of a sample of 210Bi to decay is:
A) 2.5 days
B) 3.75 days
C) 10 days
D) 15 days
E) 20 days
Q:
Starting with a sample of pure 66Cu, 7/8 of it decays into Zn in 15 minutes. The corresponding half-life is:
A) 3.75 minutes
B) 5 minutes
C) 7 minutes
D) 10 minutes
E) 15 minutes
Q:
The half-life of radium is about 1600 years. If a rock initially contains 1 g of radium, the amount left after 8000 years will be about:
A) 200 mg
B) 63 mg
C) 31 mg
D) 16 mg
E) less than 1 mg
Q:
Radioactive element A decays to the stable element B with a half-life T. Starting with a sample of pure A and no B, which graph below most correctly shows the number of A atoms, NA, as a function of time t?A) IB) IIC) IIID) IVE) V
Q:
Which expression correctly describes the radioactive decay of a substance whose half-life is T?
Q:
A large collection of nuclei are undergoing alpha decay. The rate of decay at any instant is proportional to:
A) the number of undecayed nuclei present at that instant
B) the time since the decays started
C) the time remaining before all have decayed
D) the half-life of the decay
E) the average time between decays
Q:
Possible units for the disintegration constant are:A) kg/sB) s/kgC) hourD) day-1E) cm-1
Q:
The half-life of a given nuclear disintegration A ->B:A) depends on the initial number of A atomsB) depends on the initial number of B atomsC) is an exponentially increasing function of timeD) is an exponentially decreasing function of timeE) none of the above
Q:
Two protons are about 10-10m apart. Their relative motion is chiefly determined by:A) gravitational forcesB) electrical forcesC) nuclear forcesD) magnetic forcesE) torque due to electric dipole moments
Q:
Two protons are separated by 10-16m. The nuclear (N), electrostatic (E), and gravitational (G) forces between these protons when written in order of increasing strength are:A) N, E, GB) N, G, EC) G, E, ND) G, N, EE) E, G, N
Q:
A proton in a large nucleus:
A) has a net attractive force on all other protons in the nucleus
B) has a net repulsive force on all other protons in the nucleus
C) has a net repulsive force on all other neutrons in the nucleus
D) has a net attractive force on some protons in the nucleus and a net repulsive force on others
E) has a net attractive force on some neutrons in the nucleus and a net repulsive force on others
Q:
The greatest binding energy per nucleon occurs for nuclides with masses near that of:
A) helium
B) sodium
C) iron
D) mercury
E) uranium
Q:
If a nucleus has mass M, Zprotons (mass mp) and Nneutrons (mass mn) its binding energy is equal to:A) Mc2B) (M- Zmp- Nmn)c2C) (Zmp+ Nmn- M)c2D) (Zmp+ Nmn)c2E) (Zmp- M)c2
Q:
The binding energy of a nucleus is the energy that must be supplied to:
A) remove a nucleon
B) remove an alpha particle
C) remove a beta particle
D) separate the nucleus into its constituent nucleons
E) separate the nucleus into a collection of alpha particles
Q:
1 atomic mass unit is about:A) 1.66 x10-31kgB) 9.11 x10-31kgC) 1.66 x10-27kgD) 9.11 x10-27kgE) 1.66 x10-25kg