Deck 30: Nuclear Physics

Question 1

A radioactive material initially is observed to have an activity of 1000 decays/sec. If nine hours later it is observed to have an activity of 125 decays/s, what is its half-life?

A) 1/2 hour
B) 8 hours
C) 3 hours
D) 1 hour

Answer 1

3 hours

Question 2

If there are 146 neutrons in ²³⁸U, how many neutrons are found in the nucleus of ²³³U?

A) 147
B) 145
C) 143
D) 141

Answer 2

141

Question 3

Gamma radiation is in fact which of the following?

A) electrons
B) high energy quanta
C) positrons
D) helium nuclei

Answer 3

high energy quanta

Question 4

Neglecting recoil of the gold nucleus, how much kinetic energy must an alpha particle (charge = 2 * 1.6 *10 ^{- 19} C) have to approach to within 1.95 *10 ^{- 14} m of a gold nucleus (charge = 79 * 1.6 * 10 ^{- 19} C)? (k_e = 8.99 *10⁹ N.m²/C² and 1 MeV = 1.6 *10 ^{- 13} J)

A) 14.6 MeV
B) 11.7 MeV
C) 18.2 MeV
D) 22.7 MeV

Question 5

Sample #1 is made from an isotope with decay constant and sample #2 is made from an isotope with decay constant , where . Which of the following statements must be true?

A) The activity of sample #2 is greater than that of sample #1.
B) The activity of sample #1 is greater than that of sample #2.
C) The half-life exhibited for sample #1 is greater than that of sample #2.
D) The half-life exhibited for sample #2 is greater than that for sample #1

Question 6

The relationship , where A is the mass number of a nucleus and r is it radius, implies which of the following about nuclei?

A) Nuclei are cubic.
B) Different nuclei have the same density.
C) Neutrons in nuclei attract each other even though they have no charge.
D) Nuclei tend to have the same ratio of protons to neutrons.

Question 7

The atomic number of a given element is equivalent to which of the following?

A) neutron number in the nucleus
B) sum of the protons and neutrons in the nucleus
C) proton number in the nucleus
D) number of electrons in the outer shells

Question 8

For every stable nucleus except hydrogen, if the number of nucleons is doubled, the quantity that will change least is the:

A) density.
B) mass.
C) charge.
D) volume.

Question 9

The experiment, which gave the first evidence for the existence of the atomic nucleus, involved which of the following?

A) X-ray scattering
B) cosmic ray detection
C) radioactive dating
D) alpha scattering

Question 10

The atomic mass number of a nucleus is equivalent to which of the following numbers?

A) sum of neutron and proton numbers
B) number of neutrons present
C) number of protons present
D) difference in neutron and proton numbers

Question 11

The molecular mass for chlorine is not an integer multiple of the molecular mass of hydrogen but is about 35.5 times the molecular mass of hydrogen. This is primarily because:

A) of the binding energy of the chlorine nucleus.
B) there are different isotopes of chlorine.
C) the chlorine nucleus has 35.5 nucleons.
D) the proton and neutron have different masses.

Question 12

The mass of ¹²C is 12 u, where 1 u = 1.660559 *10^-27 kg. This mass is equal to:

A) the mass of the ¹²C nucleus plus 6 electrons.
B) the mass of the ¹²C nucleus plus 12 electrons.
C) the mass of the ¹²C nucleus.
D) the mass of 6 protons and 6 neutrons.

Question 13

What potential difference is required to accelerate the nucleus of the atom , initially at rest, to a kinetic energy of 4.0 MeV?

A)
B)
C)
D)

Question 14

Alpha radiation is in fact which of the following?

A) high energy quanta
B) positrons
C) helium nuclei
D) electrons

Question 15

Rutherford's experiments involving the use of alpha particle beams directed onto thin metal foils demonstrated the existence of which of the following?

A) proton
B) neutron
C) nucleus
D) positron

Question 16

The isotope ⁶⁴Zn has a nuclear radius of 4.8 *10^-15 m. Which of the following is the mass number of an isotope for which the nuclear radius is 6.8 *10^-15 m?

A) 182
B) 125
C) 145
D) 96

Question 17

The nucleus of an atom is made up of which of the following?

A) electrons and neutrons
B) protons and neutrons
C) protons, electrons, and neutrons
D) electrons and protons

Question 18

The isotope ⁶⁴Zn has a nuclear radius of 4.8 *10^-15 m. Approximately what is the nuclear radius of the isotope ¹²⁵Te?

A) 2.0 *10^-15 m
B) 3.6 *10^-15 m
C) 2.7 * 10^-15 m
D) 6.0 *10^-15 m

Question 19

Two different nuclei emit alpha particles, the energy released in each of these decays being the same. Which of the following has the lowest resulting kinetic energy?

A) The alpha particle from the lighter nucleus.
B) The alpha particle from the heavier nucleus.
C) The heavier daughter nucleus.
D) The lighter daughter nucleus.

Question 20

Certain stars at the end of their lives are thought to collapse, combining their protons and electrons together to form a neutron star. Such a star could be thought of as a giant atomic nucleus. If a star of mass equal to M = 4.00 *10³⁰ kg collapsed into neutrons (m_n = 1.67*10^-27 kg), what would be the radius of such a star? (Hint: r = r₀A^1/3, where r₀ = 1.20 * 10^-15 m.)

A) 12.7 km
B) 25.4 km
C) 16.1 km
D) 18.5 km

Question 21

The alpha emission process results in the daughter nucleus differing in what manner from the parent?

A) Atomic mass decreases by two.
B) Atomic number increases by one.
C) Atomic mass increases by one.
D) Atomic number decreases by two.

Question 22

Tritium (³H) has a half-life of 12.3 years and releases 0.0186 MeV energy per decay. What is the activity of a 9.0-gram sample of tritium? (N_A = 6.02 *10²³ mol^-1, 1 year = 3.16 * 10⁷ s, 1 MeV = 1.6 *10^-13 J, and m_t = 3.01605 u)

A) 1.3 * 10¹⁶ Bq
B) 1.1 *10¹⁵ Bq
C) 3.6* 10¹⁴ Bq
D) 3.2 *10¹⁵ Bq

Question 23

Approximately how many half-life periods must elapse if the activity of a radioactive isotope sample is to be reduced to 0.03 of the original value?

A) 5
B) 3
C) 8
D) 60

Question 24

If a fossil bone is found to contain 1/16th as much Carbon-14 as the bone of a living animal, what is the approximate age of the fossil? (half-life of ¹⁴C = 5730 years)

A) 7640 years
B) 22,900 years
C) 45,800 years
D) 17,200 years

Question 25

A pure sample of ²²⁶Ra contains 3.0 * 10¹⁴ atoms of the isotope. If the half-life of ²²⁶Ra = 1.6 * 10³ years, what is the activity of this sample?

A) 13 * 10¹⁰ decays/yr
B) 9.4 * 10¹⁰ decays/yr
C) 6.7 * 10⁹ decays/yr
D) 8.7 *10¹⁰ decays/yr

Question 26

The beta emission process results in the daughter nucleus differing in what manner from the parent?

A) Atomic mass changes by two.
B) Atomic mass changes by one.
C) Atomic number changes by two.
D) Atomic number changes by one.

Question 27

An ancient building was known to have been built 4000 years ago. Approximately what proportion of Carbon-14 atoms are still in the building's wooden framing compared to the number which were present at the time of its construction? (half life of ¹⁴C = 5730 years)

A) 0.696
B) 0.616
C) 0.500
D) 0.425

Question 28

Chromium-55 (54.9408 u) emits an electron leaving a daughter nucleus of manganese-55 (54.9380 u). How much energy is released in this reaction? (1 u = 931.5 MeV/c²)

A) 2.61 MeV
B) 0.70 MeV
C) 5.59 MeV
D) 1.40 MeV

Question 29

Uranium-238 decays to Thorium-234 by emitting which of the following?

A) gamma ray
B) positron
C) beta particle
D) alpha particle

Question 30

Tritium is radioactive with a half-life of 12.33 years decaying into ³He with low-energy electron emission. If we have a sample of 2.35 *10¹⁹ tritium atoms, what is its activity in decays/second? (1 year = 3.16 * 10⁷ s)

A) 6.64 * 10⁷/second
B) 5.35 * 10⁹ /second
C) 3.69 * 10⁸/second
D) 4.18 *10¹⁰/second

Question 31

There are samples of two different isotopes, X and Y. Both contain the same number of radioactive atoms. Sample X has a half-life half that of Y. How do their decay rates compare?

A) The rates of X and Y are equal.
B) X has a greater rate than Y.
C) The rate depends on atomic number, not half-life.
D) X has a smaller rate than Y.

Question 32

Tritium has a half-life of 12.3 years. How many years will elapse when the radioactivity of a tritium sample diminishes to 30% of its original value?

A) 29 years
B) 21 years
C) 86 years
D) 57 years

Question 33

When radium-224 emits an alpha particle, the remaining daughter nucleus is which of the following?

A) actinium-215
B) lead-213
C) bismuth-215
D) radon-220

Question 34

Over the course of 6 hours, 15% of a radioactive material decays. What is its half-life?

A) 12.8 hrs
B) 25.6 hrs
C) 4.1 hrs
D) 68.6 hrs

Question 35

Approximately how many radioactive atoms are present in a tritium sample with an activity of 0.6 *10 ^{- 6} Ci and a half-life of 12.3 years? (1 Ci = 3.7 *10¹⁰ decays/s)

A) 4 * 10¹⁰
B) 2 * 10⁸
C) 7 *10⁸
D) 1 * 10¹³

Question 36

The half-life of radioactive Technetium-99 is 6.0 hours. Find the number of ⁹⁹Tc nuclei necessary to produce a sample of activity 18 µCi. (1 Ci = 3.7 *10¹⁰ decays/second)

A) 1.2* 10⁹
B) 3.4 * 10¹¹
C) 8.0 *10⁸
D) 2.1 * 10¹⁰

Question 37

The half-life of ¹⁹N is 0.42 s. What is the decay constant for this isotope?

A) 1.7 * 10^-11 Ci
B) 1.7 s^-1
C) 1.1 s^-1
D) The decay constant is not defined for a half-life of less than one second.

Question 38

Tritium has a half-life of 12.3 years. What proportion of its original radioactivity will a sample have after 6 years?

A) 0.55
B) 0.60
C) 0.84
D) 0.71

Question 39

A pure sample of ²²⁶Ra contains 3.0 * 10¹⁴ atoms of the isotope. If the half-life of ²²⁶Ra = 1.6 * 10³ years, what is the decay rate of this sample? (1 Ci = 3.7 * 10¹⁰ decays/s)

A) 2.7 *10^-12 Ci
B) 11 *10^-8 Ci
C) 3.4 *10^-10 Ci
D) 7.4 *10^-8 Ci

Question 40

Tritium (³H) has a half-life of 12.3 years and releases 0.0186 MeV energy per decay. What is the rate at which energy is released for a 3.0-gram sample of tritium? (N_A = 6.02 *10²³ mol^-1, 1 year = 3.16 * 10⁷ s, 1 MeV = 1.6 * 10^-13 J, and m_t = 3.01605 u)

A) 3.2 W
B) 1.1 W
C) 9.6 W
D) 0.33 W

Question 41

What particle is emitted when ²³⁶Pa decays to ²³⁶U? (The atomic numbers of Pa and U are, respectively, 91 and 92.)

A) beta (positron)
B) alpha
C) gamma quantum
D) beta (electron)

Question 42

The neutron is radioactive and can beta decay to form a proton. This can occur primarily because:

A) the neutron is neutral.
B) of the binding energy of hydrogen.
C) the proton has less mass than a neutron.
D) there are several hydrogen isotopes.

Question 43

What energy must be added or given off in a reaction where a helium atom is separated into two hydrogen atoms and two neutrons? (Atomic masses for each: hydrogen, 1.007825 u; neutron, 1.008665 u; helium, 4.002602 u; also, 1 u = 931.5 MeV/c².)

A) 28.3 MeV given off
B) 20.7 MeV added
C) 20.7 MeV given off
D) 28.3 MeV added

Question 44

Which of the following methods of decay does not result in an element different from that of the original parent nucleus?

A) alpha followed by negative beta followed by another negative beta
B) alpha followed by beta
C) alpha followed by gamma followed by another gamma
D) alpha followed by positive beta followed by another positive beta

Question 45

The energy released from a nuclear reaction is equal to:

A) energy associated with momentum conservation.
B) the exothermic endothermy.
C) energy associated with the change in mass.
D) the total charge involved.

Question 46

What particle is emitted when ²⁰Na decays to ²⁰Ne? (The atomic numbers of Na and Ne are, respectively, 11 and 10.)

A) beta (positron)
B) gamma quantum
C) alpha
D) beta (electron)

Question 47

What is the energy released for the reaction where the products are 0.0051 u less than the reactants? (1 u = 931.5 MeV/c²)

A) 7.6 MeV
B) 5.2 MeV
C) 4.8 MeV
D) 8.5 MeV

Question 48

A radioactive isotope that emits a gamma quantum will change in what respect?

A) Atomic number increases by one.
B) Atomic mass number decreases by one.
C) Atomic number decreases by one.
D) None of these choices are valid.

Question 49

If the sum total mass of reactants in a nuclear reaction is less than that of product particles, then which of the following statements best describes the conditions of the reaction?

A) reaction releases energy
B) reaction absorbs energy
C) atomic number of each reactant must be less than 80
D) atomic number of each reactant must be greater than 40

Question 50

About what fraction of the initial activity of a radioactive source remains after 10 half-lives?

A)
B)
C)
D)

Question 51

The ratio of the number of protons to neutrons in the nucleus of naturally occurring isotopes tends to vary with atomic number in what manner?

A) decreases with greater atomic number
B) increases with greater atomic number
C) remains constant for entire range of atomic numbers
D) is maximum for atomic number = 60

Question 52

A deuteron is captured by an oxygen-16 atom which in turn emits a proton. What is the element and mass number of the product isotope?

A) oxygen-15
B) fluorine-15
C) nitrogen-15
D) oxygen-17

Question 53

What is the energy released (or gained signified by the minus sign) value of the reaction ? The mass of the alpha particle is 4.002602 u, of the nitrogen is 14.003074 u, of the oxygen is 15.994915 u, and of the hydrogen is 2.014102 u. (1 u = 931.5 MeV/c²)

A) -3.11 MeV
B) -3.34 MeV
C) 3.11 MeV
D) 3.34 MeV

Question 54

The original nucleus and the final nucleus will be different isotopes of the same element for which decay scheme of the original nucleus?

A) a beta (electron) decay followed by an alpha decay
B) a beta (electron) decay followed by neutron emission
C) alpha decay followed by two beta (electron) decays
D) two gamma decays

Question 55

The isotope ²³⁸U, which starts one of the natural radioactive series, decays first by alpha decay followed by two negative beta decays. At this point, what is the resulting isotope?

A) "²³⁴Th (Z = 90 for Th.)"
B) "²³⁶U"
C) "²³⁸U"
D) "Some other uranium isotope not given above."

Question 56

In the reaction , what are the mass number and the atomic number of the product designated by X?

A) 101, 42
B) 102, 44
C) 102, 42
D) not given

Question 57

In the four radioactive series, the nuclei decay by either emitting alpha particles or beta particles until they reach the stable end product. Each decay, therefore, results in a mass number change of either 4 (for alpha decay) or 0 (for beta decay). The radium isotope ²²⁶Ra is in one of these series. What is the starting isotope in the series containing ²²⁶Ra?

A) "²³⁸U"
B) "²³⁵U"
C) "²³²Th"
D) "²³⁷Np"

Question 58

What is the binding energy per nucleon of ¹⁹⁷Au (atomic number = 79)? (The following information regarding atomic masses will be needed: ¹⁹⁷Au, 196.966543 u; hydrogen, 1.007825 u; neutron, 1.008665 u; also 1 u = 931.5 MeV/c².)

A) 8.3 MeV
B) 7.9 MeV
C) 7.7 MeV
D) 7.3 MeV

Question 59

An alpha particle (mass = 6.68 *10^-27 kg) is emitted from a radioactive nucleus with an energy of 6.22 MeV. How fast is the alpha particle moving in m/s? (1 MeV = 1.6 *10^-13 J)

A) 3.70 * 10⁶ m/s
B) 1.73 * 10⁷ m/s
C) 1.55 *10⁷ m/s
D) 1.85 * 10⁶ m/s

Question 60

A radioactive isotope that emits an alpha particle will change in what respect?

A) Atomic number decreases by four.
B) Both choices a and b are valid.
C) Mass number decreases by four.
D) None of these choices are valid.

Question 61

What is the naturally occurring isotope in a banana that gives it its radioactivity?

A)
B)
C)
D)

Question 62

One of the nuclear reactions that occurs is . What does the X represent in this equation?

A)
B)
C)
D)

Question 63

The isotope ¹⁴C cannot be used in dating old samples of which of the following?

A) a bronze implement from a cave
B) charcoal from a fire
C) a bone buried in mud
D) All of these choices can be dated using ¹⁴C.

Question 64

The mass of ²³⁸U is not quite an integer multiple of the ¹H mass. This is primarily because:

A) of the binding energy of uranium.
B) uranium is radioactive.
C) there are several isotopes of uranium.
D) the proton and neutron have different masses.

Question 65

If the stable nuclei are plotted with neutron number vs. proton number, the curve formed by the stable nuclei does not follow the line N = Z. This is predicted by examining how the binding energy is influenced by:

A) the volume of the nucleus.
B) the size of the nuclear surface.
C) the proton-neutron mass difference.
D) the Coulomb repulsion.

Question 66

Which of the following is not a unit of radiation dose?

A) rad
B) RBE
C) rem
D) none of these choices

Question 67

Calculate the binding energy per nucleon of the nucleus, given that the mass of this nucleus is 3.016029 u. (m_p = 1.007276 u, m_n = 1.008665, and 1 u = 931.5 MeV/c²)

A) 2.66 MeV/nucleon
B) 2.86 MeV/nucleon
C) 2.45 MeV/nucleon
D) 2.23 MeV/nucleon

Question 68

A 1-gram sample of wood is taken from an ancient site. If the Carbon-14 activity of the sample is 12.5% that of present-day organic material, what is the age of the wood? (T_1/2 for ¹⁴C is 5730 years.)

A) 8600 years
B) 4460 years
C) 11,500 years
D) 17,200 years

Question 69

A rad is that amount of radiation that:

A) is also known as a rem.
B) deposits 10^-2 J of energy into 1 kg of absorbing material.
C) deposits 8.76*10^-3 J of energy into 1 kg of air.
D) produces 2.08 *10⁹ ion pairs per cm³ in air under standard conditions.

Question 70

The binding energy of a nucleus is equal to:

A) the mass of the nucleus times c².
B) the energy needed to separate all the nucleons from each other.
C) the average energy with which any nucleon is bound in the nucleus.
D) the energy needed to remove one of the nucleons.