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39. 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 of its initial decay rate?

A. 35

B. 105

C. 187

D. 210

E. 280

ans: E

40. 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

ans: E

41. 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

ans: A

42. 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, Z − 2

B. A − 2, Z − 2

C. A − 2, Z

D. A − 4, Z

E. A − 4, Z − 2

ans: E

43. Radioactive polonium,

214

Po (Z = 84), decays by alpha emission to:

214

Po (Z = 84)

210

Pb (Z = 82)

214

At (Z = 85)

218

Po (Z = 84)

210

Bi (Z = 83)

ans: B

Chapter 42: NUCLEAR PHYSICS 631

44. A radium atom,

226

Ra (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

ans: A

45. 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

ans: C

46. In an alpha decay the disintegration energy appears chieﬂy 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

ans: B

47. Rank the following collections of particles according to the total binding energy of all the

particles in each collection, least to greatest.

collection 1:

244

Pu (Z = 94) nucleus alone

collection 2:

240

U(Z = 92) nucleus, α particle

collection 3:

240

U(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

ans: D

48. 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

ans: B

632 Chapter 42: NUCLEAR PHYSICS

49. Beta particles from various radioactive sources all have:

A. the same mass

D. the same speed

B. the same charge

E. the same deﬂection

C. the same energy in a magnetic ﬁeld

ans: A

50. A radioactive atom X emits a β

−

particle. The resulting atom:

A. must be very reactive chemically

B. has an atomic number that is one more than that of X

C. has a mass number that is one less than that of X

D. must be radioactive

E. is the same chemical element as X

ans: B

51. A nucleus with mass number A and atomic number Z undergoes β

−

decay. The mass number

and atomic number, respectively, of the daughter nucleus are:

A. A, Z − 1

B. A − 1, Z

C. A +1,Z − 1

D. A, Z +1

E. A, Z − 1

ans: D

52. A nucleus with mass number A and atomic number Z undergoes β

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

ans: E

53. 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

ans: B

Chapter 42: NUCLEAR PHYSICS 633

54. The energies of electrons emitted in β

−

decays have a continuous spectrum because:

A. the original neutron has a continuous spectrum

B. a neutrino can carry oﬀ energy

C. the emitted electron is free

D. energy is not conserved

E. the daughter nucleus may have any energy

ans: B

55. If

204

Tl (Z = 81) emits a β

−

particle from its nucleus:

A. stable Tl is formed

202

Hg (Z = 80) is formed

204

Pb (Z = 82) is formed

D. radioactive Tl is formed

197

Au (Z = 79) is formed

ans: C

56. An atom of

235

U(Z = 92) disintegrates to

207

Pb (Z = 82) with a half-life of about a billion

years by emitting seven alpha particles and β

−

particles:

A. 3

B. 4

C. 5

D. 6

E. 7

ans: B

57. When ordinary sodium (

Na, Z = 11) is bombarded with deuterons, the products are a

neutron and:

Al, Z =13

Na, Z =11

Mg, Z =12

Ne, Z =10

ans: D

58.

Cu can be turned into

Cu, with no accompanying product except a gamma, if bombarded

with:

A. protons

B. neutrons

C. deuterons

D. electrons

E. alpha particles

ans: B

634 Chapter 42: NUCLEAR PHYSICS

59. Magnesium has atomic number 12, hydrogen has atomic number 1, and helium has atomic

number 2. In the nuclear reaction

Mg +

H → ()+

He the missing quantity is:

Na (Z = 11)

Ne (Z = 10)

Na (Z = 11)

Ne (Z = 10)

Na (Z = 11)

ans: E

60. Aluminum has atomic number 13, helium has atomic number 2, and silicon has atomic number

14. In the nuclear reaction

Al +

He →

Si + ( ) the missing particle is:

A. an α particle

B. a positron

C. an electron

D. a proton

E. a neutron

ans: D

61. The

Cu (Z = 29) produced in a nuclear b ombardment is unstable, changing to

Zn (Z = 30)

by the emission of:

A. a proton

B. a gamma ray photon

C. a positron

D. an electron

E. an alpha particle

ans: D

62. When ordinary sulfur,

S(Z = 16), is bombarded with neutrons, the products are

P(Z = 15)

and:

A. alpha particles

B. protons

C. deuterons

D. gamma ray particles

E. electrons

ans: B

63. A certain nucleus, after absorbing a neutron, emits a β

−

and then splits into two alpha particles.

The (A, Z) of the original nucleus must have been:

A. 6, 2

B. 6, 3

C. 7, 2

D. 7, 3

E. 8, 4

ans: D

Chapter 42: NUCLEAR PHYSICS 635

64. When

Na (Z = 11) is bombarded with protons, the products are

Ne (Z = 10) and:

A. a neutron

B. an alpha particle

C. a deuteron

D. a gamma ray particle

E. two beta particles

ans: B

65. Bombardment of

Si (Z = 14) with alpha particles may produce:

A. a proton and

P(Z = 15)

B. hydrogen and

S(Z = 16)

C. a deuteron and

Al (Z = 13)

D. helium and

P(Z = 15)

Cl (Z = 17)

ans: A

66. 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

ans: A

67. 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 per unit mass of target delivered by radiation to a target

D. the biological eﬀect of radiation

E. none of the above

ans: C

68. 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

ans: D

636 Chapter 42: NUCLEAR PHYSICS

Chapter 43: ENERGY FROM THE NUCLEUS

1. If the nucleus of a lead atom were broken into two identical nuclei, the total mass of the

resultant nuclei would be:

A. the same as before

B. greater than before

C. less than before

D. converted into radiation

E. converted into kinetic energy

ans: C

2. 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

235

U ﬁssion

4. energy needed to remove a neutron from a

C nucleus

Rank them in order of increasing value.

A. 1, 2, 3, 4

B. 1, 3, 2, 4

C. 1, 2, 4, 3

D. 2, 1, 4, 3

E. 2, 4, 1, 3

ans: C

3. The binding energy per nucleon:

A. increases for all ﬁssion events

B. increases for some, but not all, ﬁssion events

C. decreases for all ﬁssion events

D. decreases for some, but not all, ﬁssion events

E. remains the same for all ﬁssion events

ans: A

4. 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

ans: E

Chapter 43: ENERGY FROM THE NUCLEUS 637

5. 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

ans: B

6. 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

ans: A

235

U is readily made ﬁssionable by a thermal neutron but

238

U is not because:

A. the neutron has a smaller binding energy in

236

B. the neutron has a smaller excitation energy in

236

C. the potential barrier for the fragments is less in

239

D. the neutron binding energy is greater than the barrier height for

236

U and less than the

barrier height for

239

E. the neutron binding energy is less than the barrier height for

236

U and greater than the

barrier height for

239

ans: D

8. An explosion does not result from a small piece of

235

U because:

A. it does not ﬁssion

B. the neutrons released move too fast

238

U 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

ans: D

9. When

236

U ﬁssions the fragments are:

A. always

140

Xe and

B. always identical

C. never

140

Xe and

D. never identical

E. none of the above

ans: E

638 Chapter 43: ENERGY FROM THE NUCLEUS

10. Fission fragments usually decay by emitting:

A. alpha particles

B. electrons and neutrinos

C. positrons and neutrinos

D. only neutrons

E. only electrons

ans: B

11. When

236

U ﬁssions, the products might be:

146

Ba,

Kr, and a proton

146

Ba,

Kr, and a neutron

148

Cs and

133

Sr, and an alpha particle

E. two uranium nuclei

ans: B

12. 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

ans: E

13. Which one of the following represents a ﬁssion reaction that can be activated by slow neutrons?

238

→

146

239

→

141

238

→

234

→

107

→

108

→

108

−1

ans: B

14. In the uranium disintegration series:

A. the emission of a β

−

particle increases the mass number A by one and decreases the atomic

number Z by one

B. the disintegrating element merely ejects atomic electrons

C. the emission of an α particle decreases the mass number A by four and decreases the atomic

number Z by two

D. the nucleus always remains unaﬀected

E. the series of disintegrations continues until an element having eight outermost orbital elec-

trons is obtained

ans: C

Chapter 43: ENERGY FROM THE NUCLEUS 639

15. Separation of the isotopes of uranium requires a physical, rather than chemical, method be-

cause:

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%

235

E. uranium is the heaviest element in nature

ans: B

16. Which one of the following is NOT needed in a nuclear ﬁssion reactor?

A. Moderator

B. Fuel

C. Coolant

D. Control device

E. Accelerator

ans: E

17. 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

ans: D

18. 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. 1/2

B. 1/4

C. 2

D. 4

E. 1

ans: E

19. The purpose of a moderator in a nuclear reactor is to:

A. provide neutrons for the ﬁssion pro cess

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

ans: B

640 Chapter 43: ENERGY FROM THE NUCLEUS