Question 1

The sodium atom has an atomic number of 11 and an atomic weight of 23. The neutral atom contains

Accepted Answer

A)   11 neutrons and 12 protons.
B)   11 protons and 12 neutrons.
C)   12 electrons and 11 neutrons.
D)   23 protons and 12 electrons.
E)   23 electrons and 12 neutrons.

Question 2

A radioactive source has a half-life of 2 min. At time t = 0 it is placed near a detector and the counting rate is observed to be 3000 counts/s. If the detection efficiency is 25%, how many radioactive nuclei are there at time t = 2 min?

Accepted Answer

A)   1.04 × 106
B)   1.67 × 106
C)   2.08 × 106 
D)   3.41 × 106
E)   3.79 × 106

Question 3

A radioactive substance in the laboratory has a half-life of 8 h. At noon today, a Geiger counter reads 480 counts/min above background. At noon tomorrow, the counter should read about

Accepted Answer

A)   480 counts/min.
B)   240 counts/min.
C)   120 counts/min.
D)   60 counts/min.
E)   30 counts/min.

Question 4

A moderator is used to slow

Accepted Answer

A)   protons.
B)   alpha particles.
C)   neutrons.
D)   beta particles.
E)   photons.

Question 5

The pair of nuclides that represents isotopes is

Accepted Answer

A)    .
B)    .
C)    .
D)    .
E)    .

Question 6

A radiologist uses a radioactive isotope of iodine, 123I, for thyroid scans. She receives a shipment of 15 mCi of this isotope at noon on a Tuesday. The half-life of this isotope is 13.2 h. What is the decay rate at noon on Thursday of the same week?

Accepted Answer

A)   12 mCi
B)   1.2 mCi
C)   2.4 mCi
D)   4.2 mCi
E)   24 mCi

Question 7

The graph shows the activity as a function of time for a radioisotope. The half-life of this particular radioisotope is approximately

Accepted Answer

A)   5 h.
B)   4 h.
C)   8 h.
D)   20 h.
E)   10 h.

Question 8

The decay rate of a radioactive sample is defined as the number of decays per second. For a sample with N particles and a decay constant  λ\lambdaλ , the decay rate is

Accepted Answer

A)   proportional to  λ\lambdaλ  and inversely proportional to N.
B)   proportional to  λ\lambdaλ  but independent of N.
C)   directly proportional to both  λ\lambdaλ  and N.
D)   independent of  λ\lambdaλ  but proportional to N.
E)   inversely proportional to both  λ\lambdaλ  and N.

Question 9

06 d it has a decay rate of 7.5 mCi. The half-life of 32P is approximately

Accepted Answer

A)   3.03 d.
B)   7.30 d.
C)   12.1 d.
D)   14.6 d.
E)   24.2 d.

Question 10

The radius of the 63Cu nucleus is approximately

Accepted Answer

A)   0.382 fm.
B)   4.78 fm.
C)   12.1 fm.
D)   24.2 fm.
E)   100 fm.

Question 11

Cesium-137 has a half-life of 31.0 y. The time required for the cesium-137 now present to decrease to 1/30 its present value is

Accepted Answer

A)   930 y.
B)   30 y.
C)   465 y.
D)   152 y.
E)   1.6 y.

Question 12

A nuclear proton is changed into a neutron when

Accepted Answer

A)   positrons are emitted.
B)   positrons are absorbed.
C)   electrons are emitted.
D)   neutrons are absorbed.
E)   protons are emitted.

Question 13

The control rods in a nuclear reactor are used to

Accepted Answer

A)   produce neutrons.
B)   add fuel to the reactor.
C)   fragment elements by fission.
D)   absorb γ rays.
E)   absorb neutrons.

Question 14

In gamma decay a nucleus in an excited state decays to a lower energy state by the emission of a high-energy photon called a gamma ray. Which of the following statements is true?

Accepted Answer

A)   Gamma decay is always slow greater than a ns) .
B)   Gamma decay is always fast less than a ns) .
C)   Gamma decay is usually fast but can in special cases be slow.
D)   Gamma decay is always accompanied by the emission of a neutrino.
E)   Gamma decay is always accompanied by the emission of a β particle.

Question 15

Nuclear fusion takes place when

Accepted Answer

A)   a large nucleus splits into two fragments with the release of a few neutrons.
B)   an α particle is ejected from the nucleus.
C)   a positive β particle is ejected from the nucleus.
D)   small nuclei combine to form a larger one.
E)   heavy hydrogen is accelerated.

Question 16

Why is the ratio of neutrons to protons greater in the heavier elements?

Accepted Answer

A)   The greater the number of protons, the weaker the proton-neutron strong nuclear force.
B)   The greater the number of neutrons, the weaker the proton-neutron strong nuclear force.
C)   The greater the number of protons, the greater the electrostatic force of repulsion.
D)   The greater the number of neutrons, the greater the electrostatic force of repulsion.
E)   There is actually a lesser ratio of neutrons to protons in the heavier elements.

Question 17

1 d it has a decay rate of 4.25 mCi. The half-life of 32P is approximately

Accepted Answer

A)   3.03 d.
B)   7.30 d.
C)   12.1 d.
D)   14.6 d.
E)   24.2 d.

Question 18

Estimate the mass density of the nucleus of an atom.

Accepted Answer

A)   103 kg/m3
B)   106 kg/m3
C)   109 kg/m3 
D)   1014 kg/m3
E)   1017 kg/m3

Question 19

A radioactive sample is detected to produce 2500 decays per minute at 6:00 p.m. and 150 decays per minute at 11:00 p.m. the same day. What is the half-life of the sample?

Accepted Answer

A)   2.81 hrs
B)   0.56 hrs
C)   1.23 hrs
D)   1.77 hrs
E)   0.89 hrs

Question 20

A particle is incident on a nucleus. The particle

Accepted Answer

A)   can be scattered elastically by the nucleus.
B)   can be scattered inelastically by the nucleus with the nucleus in an excited state.
C)   can be absorbed by the nucleus completely.
D)   can be absorbed by the nucleus and other particles)  emitted.
E)   All of the above are possible.

Exam 27: Nuclear Physics

A nuclear proton is changed into a neutron when

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The pair of nuclides that represents isotopes is

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1 d it has a decay rate of 4.25 mCi. The half-life of 32P is approximately

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Why is the ratio of neutrons to protons greater in the heavier elements?

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Nuclear fusion takes place when

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Estimate the mass density of the nucleus of an atom.

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A radiologist uses a radioactive isotope of iodine, 123I, for thyroid scans. She receives a shipment of 15 mCi of this isotope at noon on a Tuesday. The half-life of this isotope is 13.2 h. What is the decay rate at noon on Thursday of the same week?

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A moderator is used to slow

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The decay rate of a radioactive sample is defined as the number of decays per second. For a sample with N particles and a decay constant λ\lambdaλ , the decay rate is

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In gamma decay a nucleus in an excited state decays to a lower energy state by the emission of a high-energy photon called a gamma ray. Which of the following statements is true?

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A radioactive sample is detected to produce 2500 decays per minute at 6:00 p.m. and 150 decays per minute at 11:00 p.m. the same day. What is the half-life of the sample?

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The graph shows the activity as a function of time for a radioisotope. The half-life of this particular radioisotope is approximately

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A particle is incident on a nucleus. The particle

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Cesium-137 has a half-life of 31.0 y. The time required for the cesium-137 now present to decrease to 1/30 its present value is

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A radioactive source has a half-life of 2 min. At time t = 0 it is placed near a detector and the counting rate is observed to be 3000 counts/s. If the detection efficiency is 25%, how many radioactive nuclei are there at time t = 2 min?

Correct AnswerverifiedShow Answer

The sodium atom has an atomic number of 11 and an atomic weight of 23. The neutral atom contains

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06 d it has a decay rate of 7.5 mCi. The half-life of 32P is approximately

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The control rods in a nuclear reactor are used to

Correct AnswerverifiedShow Answer

A radioactive substance in the laboratory has a half-life of 8 h. At noon today, a Geiger counter reads 480 counts/min above background. At noon tomorrow, the counter should read about

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The radius of the 63Cu nucleus is approximately

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Correct Answer
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1 d it has a decay rate of 4.25 mCi. The half-life of ³²P is approximately

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A radiologist uses a radioactive isotope of iodine, ¹²³I, for thyroid scans. She receives a shipment of 15 mCi of this isotope at noon on a Tuesday. The half-life of this isotope is 13.2 h. What is the decay rate at noon on Thursday of the same week?

Correct Answer
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Correct Answer
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The decay rate of a radioactive sample is defined as the number of decays per second. For a sample with N particles and a decay constant $\lambda$ , the decay rate is

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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06 d it has a decay rate of 7.5 mCi. The half-life of ³²P is approximately

Correct Answer
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Correct Answer
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Correct Answer
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The radius of the ⁶³Cu nucleus is approximately

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