Physics 195C
Professor Siegel
Practice Exam
Chapter 27,40






1. The smallest particle of any chemical element that can exist by itself and yet retain the qualities that distinguish it as that element is:
A.an electron
B.a proton
C.a neutron
D.an atom
E.a molecule


2. Of the following which has the smallest rest energy?
A.A neutron
B.An electron
C.An ion
D.A proton
E.An atom


3. The mass of a neutron:
A.equals that of an electron
B.equals that of a proton
C.is a little more than that of a proton
D.is exactly that of a proton plus an electron
E.is as yet unmeasured


4. 1 atomic mass unit is about:
A.1.66 × 10–31 kg
B.9.11 × 10–31 kg
C.1.66 × 10–27 kg
D.9.11 × 10–27 kg
E.1.66 × 10–25 kg


5. The atomic number of an element is:
A.the whole number nearest to its mass
B.the number of protons in its nucleus
C.the nearest whole number of hydrogen atoms having the same mass as a single atom of the given element
D.the number of neutrons in its nucleus
E.its order of discovery


6. Iron has atomic number 26. Naturally mined iron contains isotopes of mass numbers 54, 56, 57, and 58. Which of the following statements is FALSE?
A.every atom of iron has 26 protons
B.some iron atoms have 30 neutrons
C.some iron atoms have 54 neutrons
D.the isotopes may be separated in a mass spectrometer
E.there are four kinds of naturally occurring iron atoms with the same chemical properties


7. Let Z denote the atomic number and A denote the mass number of a nucleus. The number of neutrons in this nucleus is:
A.Z
B.A – Z
C.A – 2Z
D.A
E.2A – Z


8. The isotopes of an element:
A.cannot be separated at all
B.occur well separated in nature
C.have similar chemical behavior
D.cannot be separated by physical methods
E.have equal masses


9. Volumes of atomic nuclei are proportional to:
A.the mass number
B.the atomic number
C.the total nuclear spin
D.the number of neutrons
E.none of these


10. A femtometer is:
A.larger than 10–9 m
B.10–9 m
C.10–12 m
D.10–15 m
E.10–18 m


11. A nucleus with a mass number of 64 has a mean radius of about:
A.4.8 fm
B.19 fm
C.77 fm
D.260 fm
E.2.6 × 105 fm


12. A proton in a large nucleus:
A.attracts all other protons
B.repels all other protons
C.repels all neutrons
D.attracts some protons and repels others
E.attracts some neutrons and repels others


13. Two protons are separated by 10–16 m. The nuclear (N), electrostatic (E), and gravitational (G) forces between these protons when written in order of increasing strength are:
A.E, N, G
B.N, G, E
C.G, E, N
D.G, N, E
E.E, G, N


14. 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


15. If a nucleus has mass M, Z protons (mass mp) and N neutrons (mass mn) its binding energy is equal to:
A.Mc2
B.(M – Zmp – Nmn)c2
C.(Zmp + Nmn – M)c2
D.(Zmp + Nmn)c2
E.(Zmp – M)c2


16. Stable nuclei generally:
A.have a greater number of protons than neutrons
B.have low mass numbers
C.have high mass numbers
D.are beta emitters
E.none of the above


17. The greatest binding energy per nucleon occurs for nuclides with masses near that of:
A.helium
B.sodium
C.iron
D.mercury
E.uranium


18. 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


19. Which expression correctly describes the radioactive decay of a substance whose half-life is T?
A.N(t) = N0e–(t ln2)/T
B.N(t) = N0e–t/T
C.N(t) = N0e–tT
D.N(t) = N0e–tT ln2
E.N(t) = N0e–t/T ln2


20.

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 correctly shows the number of A atoms, NA, as a function of time t?




A.I
B.II
C.III
D.IV
E.V


21. A large collection of nuclei are undergoing alpha decay. The rate of decay at any instant is:
A.proportional to the number of undecayed nuclei present at that instant
B.proportional to the time since the decays started
C.proportional to the time remaining before all have decayed
D.proportional to the half-life of the decay
E.a universal constant


22. The relation between the disintegration constant l and the half-life T of a radioactive substance is:
A.l = 2T
B.l = 1/T
C.l = 2/T
D.lT = ln 2
E.lT = ln(1/2)


23. Possible units for the decay constant l are:
A.kg/s
B.s/kg
C.hour
D.day–1
E.cm–1


24. The half-life of a given nuclear disintegration A ® B:
A.depends on the initial number of A atoms
B.depends on the initial number of B atoms
C.is an exponentially increasing function of time
D.is an exponentially decreasing function of time
E.none of the above


25.

The graph shows the activity R as a function of the time t for 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


26. 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


27. Starting with a sample of pure 66Cu, 7/8 of it decays into Zn in 15 minutes. The corresponding half-life is:
A.15 minutes
B.5 minutes
C.7 minutes
D.3.75 minutes
E.10 minutes


28. 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.10 days
C.15 days
D.20 days
E.3.75 days


29. Radioactive 90Sr has a half-life of 30 years. What percent of a sample of 90Sr will remain after 60 years?
A.0%
B.25%
C.50%
D.75%
E.14%


30. The half-life of a radioactive isotope is 6.5 h. If there are initially 48 × 1032 atoms of this isotope, the number of atoms of this isotope remaining after 26 h is:
A.12 × 1032
B.6 × 1032
C.3 × 1032
D.6 × 104
E.3 × 102


31. 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
B.105
C.187
D.210
E.280


32. Of the three common types of radiation (alpha, beta, gamma) from radioactive sources, electric charge is carried by:
A.only beta and gamma
B.only beta
C.only alpha and gamma
D.only alpha
E.only alpha and beta


33. 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


34. A nucleus with mass number A and atomic number Z emits an alpha particle. The mass number and atomic number, respectively, of the daughter nucleus are:
A.A + 2, Z + 2
B.A – 2, Z – 2
C.A – 2, Z
D.A – 4, Z
E.A – 4, Z – 2


35. 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)


36. 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


37. 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


38.

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) nuceus alone


collection 2: 240U (Z = 92) nucleus, a particle


collection 3: 240U (Z = 92) nucleus, two separated protons, two separated neutrons


A.1,2,3
B.3,2,1
C.2,1,3
D.1,3,2
E.2,3,1


39. 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


40. A radioactive atom X emits a b – particle. The resulting atom:
A.must be very reactive chemically
B.has a Z one more than that of X
C.has an A one less than that of X
D.must be radioactive
E.is the same chemical element as X


41. A nucleus with mass number A and atomic number Z undergoes b – 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


42. A nucleus with mass number A and atomic number Z undergoes b + 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


43. 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


44. If 204Tl (Z = 81) emits a b – particle from its nucleus:
A.stable Tl is formed
B.202Hg (Z = 80) is formed
C.204Pb (Z = 82) is formed
D.radioactive Tl is formed
E.197Au (Z = 79) is formed


45. 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 ______ b – particles:
A.3
B.4
C.5
D.6
E.7


46. 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


47. In a pure metal the collisions that are characterized by the mean free time 0 in the expression for the resistivity are chiefly between:
A.electrons and other electrons
B.electrons with energy about equal to the Fermi energy and atoms
C.all electrons and atoms
D.electrons with energy much less than the Fermi energy and atoms
E.atoms and other atoms


48. A certain metal has 5.3 × 1029 conduction electrons/m3, with a mean time between collisions of 3.6 × 10–14 s. Its resistivity is about:
A.3.4 × 10–25 W × m
B.6.8 × 10–12 W × m
C.1.9 × 10–9 W × m
D.3.6 × 10–6 W × m
E.5.4 ×108 W × m


49. The Fermi-Dirac probability function P(E) varies between:
A.0 and 1
B.0 and infinity
C.1 and infinity
D.–1 and 1
E.0 and EF


50. For a metal at absolute temperature T, with Fermi energy EF, the occupancy probability is given by:
A.
B.
C.
D.
E.


51. In a metal at 0 K, the Fermi energy is:
A.the highest energy of any electron
B.the lowest energy of any electron
C.the mean thermal energy of the electrons
D.the energy of the top of the valence band
E.the energy at the bottom of the conduction band


52. The occupancy probability for a state with energy equal to the Fermi energy is:
A.0
B.0.5
C.1
D.1.5
E.2


53. Ther Fermi energy of a metal depends primarily on:
A.the temperature
B.the volume of the sample
C.the strength of the applied electric field
D.the strength of the applied magnetic field
E.the number density of conduction electrons


54. The ratio vF/vd of the Fermi speed to the drift speed of an electron involved with the conduction of electricity in copper is of the order:
A.107
B.10–7
C.1
D.1020
E.10–20


55. At T = 0 K the probability that a state 0.50 eV below the Fermi level is occupied is about:
A.0
B.5.0 × 10–9
C.5.0 × 10–6
D.5.0 × 10–3
E.1


56. At T = 0 K the probability that a state 0.50 eV above the Fermi level is occupied is about:
A.0
B.5.0 × 10–9
C.5.0 × 10–6
D.5.0 × 10–3
E.1


57. At room temperature kT is about 0.0259 eV. The probability that a state 0.50 eV above the Fermi level is occupied at room temperature is:
A.1
B.0.05
C.0.025
D.5.0 × 10–6
E.4.1 × 10–9


58. For a metal at room temperature the temperature coefficient of resistivity is determined primarily by:
A.the number of electrons in the conduction band
B.the number of impurity atoms
C.the binding energy of outer shell electrons
D.collisions between conduction electrons and atoms
E.none of the above


59. Superconductivity works via
A.Bardeen pairs
B.Cooper Pairs
C.Onnes Pairs
D.Schriffer pairs


60. A contact potential will exist
A.any time 2 metals are in contact
B.only when the 2 metals have the same Fermi Energy
C.only when the two metals have different Fermi Energies
D.only when the Threshold Wavelengths are equal


61. Applying an electric field across a conductor
A.does not affect the Fermi Energy
B.does affect the Fermi Energy
C.affects the Fermi Factor
D.all of the above


62. Applying an electric field across a conductor
A.shifts the Fermi Velocity in the positive direction
B.shifts the Fermi Velocity in the negative direction
C.lowers the Fermi factor
D.B and C


63. In the classical description of conduction, the Mean Free Path
A.depends on the temperature of the material
B.depends on the radius of the lattice ions
C.depends on the electric field applied
D.all of the above


64. In the Quantum description of conduction, the Mean Free Path
A.depends on the electron linear density
B.depends on the lattice ion radius
C.depends on the Fermi energy
D.depends on the temperature


65. Fermions
A.have an integer spin quantum number
B.have a zero spin quantum number
C.have a fractional spin quantum number
D.have (+/- )n spin quantum number


66. The total energy of 3 Bosons placed in the E2 energy level is
A.3E1
B.2E1 + E2
C.3E2
D.2E2 + E3


67. The total energy of 3 Fermions placed in the E2 energy level is

A.3E1
B.2E1 + E2
C.3E2
D.2E2 + E3


68. Which particles obey the Pauli Exclusion Principle
A.Bosons
B.Fermions
C.electrons only
D.protons and neutrons only



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