The following are statements concerning radioactive decay. I.
Alpha particles have discrete energies.
II.
The beta-energy spectrum is a broad continuous distribution of energies.
III.
Gamma rays are emitted with discrete energies.
Which statement(s) is(are) evidence for the existence of nuclear energy levels? A.
I only
B.
II only
C.
III only
D.
I and III only (1)
2.
The activity of a sample of Iodine-131 is plotted as a function of time as shown below. The activity scale is logarithmic. 10000 9000 8000 7000 6000 5000 4000 3000
2000
Activity / Bq
1000
900 800 700 600 500 400 300
200
100
0
10
20
30
40
50 60 time / days
The half-life of Iodine-131 is close to A.
180 days.
B.
55 days.
C.
28 days.
D.
8 days. (1)
1
3.
Which one of the following is a correct definition of the decay constant of a radio-isotope? A.
The constant of proportionality linking half-life to rate of decay of nuclei.
B.
The constant of proportionality linking decay rate to number of undecayed nuclei.
C.
The reciprocal of the half-life of the radio-isotope.
D.
The rate of decay of nuclei in a fresh sample of the radio-isotope. (1)
4.
Which one of the following gives evidence for the existence of nuclear energy levels? A.
Alpha particle scattering
B.
Gamma ray spectra
C.
Photoelectric effect
D.
Matter waves (1)
5. The nucleus decay are
30 P 15
undergoes radioactive decay to the nucleus
A.
a positron and an antineutrino.
B.
an electron and an antineutrino.
C.
a positron and a neutrino.
D.
an electron and a neutrino.
30 Si. 14
The particles emitted in the
(1)
6.
Which one of the following statements is true for the decay of a radioactive isotope? A.
The activity at any particular time is proportional to the original number of nuclei present.
B.
The activity at any particular time is proportional to the number of nuclei of the isotope present at that time.
C.
The activity at any particular time is proportional to the half-life of the isotope.
D.
The activity at any particular time is proportional to the decay constant of the isotope. (1)
7.
Which one of the following gives evidence for the existence of nuclear energy levels? A.
Gamma ray spectra
B.
Visible line spectra
C.
Absorption spectra
D.
X-ray spectra (1)
2
8.
The decay constant λ in radioactive decay is defined as A.
the probability of decay per unit time of a nucleus.
B.
the probability of decay of a nucleus.
C.
ln 2 where T 1 is the half-life. the constant T 1 2 2
D.
the constant in the radioactive decay equation N = N0e–λt. (1)
9.
The spectrum of energy of β–-particles emitted in radioactive decay is explained on the basis of A.
the emission of neutrinos during the decay process.
B.
the emission of antineutrinos during the decay process.
C.
the absorption of neutrinos during the decay process.
D.
the absorption of antineutrinos during the decay process. (1)
10.
Which of the following graphs shows the variation with mass m of the activity of a sample of a radioactive material?
A.
B.
activity
activity
m C.
m D.
activity
m
activity
m (1)
3
11.
Which of the following correctly describes the nature of the energy spectra of alpha (α), beta (β) and gamma (γ) radiation?
α
β
γ
A.
discrete
continuous
discrete
B.
continuous
discrete
discrete
C.
discrete
discrete
continuous
D.
continuous
continuous
discrete (1)
40 12. A nucleus of the isotope potassium-40 40 19 K decays to form a nucleus argon-40 18 Ar Which one of the following correctly identifies the other two particles resulting from this decay?
A.
− and v
B.
− and v
C.
+ and v
D.
+ and v (1)
13.
14.
The decay constant of two nuclei is . One nucleus decays within a time interval of one second. The probability of decay of the other nucleus in the same time interval is A.
0.
B.
λ . 2
C.
.
D.
2.
Which one of the following best shows a possible path of an -particle as it is deflected by a stationary gold nucleus? A.
B.
C.
D.
(1) 4
15.
A sample of a radioactive isotope of half-life T 1 initially contains N atoms. Which one of the 2
following gives the number of atoms of this isotope that have decayed after a time 3T 1 ? 2
A.
1 N 8
B.
1 N 3
C.
2 N 3
D.
7 N 8 (1)
16.
The decay constant of a radioactive isotope is 0.02 s−1. Which one of the following statements about this isotope is true?
1 s. 0.02
A.
The half-life of the isotope is
B.
In 1 s, 0.02 nuclei will decay.
C.
A nucleus decays in every 0.02 s.
D.
The probability that a nucleus will decay in 1 s is 0.02. (1)
17.
A radioactive isotope has a half-life of five minutes. A particular nucleus of this isotope has not decayed within a time interval of five minutes. A correct statement about the next five minute interval is that this nucleus A.
has a lower than 50 chance of decaying.
B.
will certainly decay.
C.
has a 50 chance of decaying.
D.
has a better than 50 chance of decaying. (1)
18.
A correct statement about nuclei is that most have approximately the same A.
radius.
B.
density.
C.
binding energy.
D.
neutron to proton ratio. (1)
5
19.
A nucleus of potassium-40 undergoes + decay to an excited state of a nucleus of argon-39. The argon-39 then reaches its ground state by the emission of a -ray photon. The diagram represents the + and energy level diagram for this decay process.
ground state energy level of potassium–40
+
X excited energy level of argon–39 ground state energy level of argon–39 The particle represented by the letter X is A.
an antineutrino.
B.
a neutrino.
C.
an electron.
D.
a photon. (1)
20.
The rest-mass of a nucleus of lithium-7 73 Li is mL. The rest-mass of a proton is mP and the restmass of a neutron is mN. The speed of light in free space is c.
Which of the following is a correct expression for the binding energy of a lithium-7 nucleus? A.
(3mP + 4mN – mL)c2
B.
(3mP + 4mN + mL)c2
C.
(4mP + 3mN – mL)c2
D.
(3mP + 7mN – mL)c2 (1)
21.
The masses of nuclei in a sample of uranium are determined using a mass spectrometer. Measurements suggest that some nuclei in the sample have double the mass of others. Which of the following is the most likely explanation for this observation? A.
Uranium nuclei are decaying radioactively.
B.
Several uranium isotopes are present.
C.
The uranium ions have different speeds.
D.
The uranium ions have different charges. 6
22.
The probability of decay in one second of a radioactive nucleus is λ. During a particular onesecond interval, a nucleus does not decay. What is the probability of decay of this nucleus during the next one-second interval? A.
1 λ
B.
C.
2
D.
2 (1)
23.
The decay constant of a nuclide with a long half-life may be determined using the equation activity = number of nuclei present. Which of the following is the best explanation as to why this equation may be used? A.
The decay constant is very large.
B.
The number of nuclei in a sample decreases rapidly.
C.
The activity of the sample decreases slowly.
D.
The sample contains a large number of nuclei. (1)
24.
A freshly prepared sample of a radioactive isotope contains N0 atoms. The decay constant of the isotope is . The initial activity of the sample is A.
N0 . λ
B.
N 0 ln 2 . λ
C.
N0.
D.
N0e−. (1)
25.
A nucleus of sodium 22 decay into a nucleus of neon (Ne). 11 Na undergoes beta-plus Which of the following is the correct nuclear reaction for this decay? 0 0v
A.
22 22 11 Na 12 Ne
0 1 e
B.
22 22 11 Na 10 Ne
0 1 e
00 v
C.
22 22 11 Na 10 Ne
0 1 e
D.
22 22 0 11 Na 12 Ne 1 e
0 0v
00 v 7
26.
One possible fission reaction can be represented by the equation 236 135 98 1 92 U 52Te 40 Zr 3 0 n.
EU, ETe and EZr are the binding energies of uranium, tellurium and zirconium respectively. Binding energy is defined as a positive quantity. It may be deduced that A.
EU = ETe + EZr.
B.
EU ETe + EZr.
C.
EU ETe + EZr.
D.
EU = ETe − EZr. (1)
27.
The diameter of a nucleus may be estimated from A.
determinations of half-life.
B.
gamma-ray spectra.
C.
charged particle scattering experiments.
D.
fusion and fission reactions. (1)
28.
The ratio of mass-to-charge was measured for a sample of a pure element in a mass spectrometer. The values obtained were 17.5
where
m q
18.5
m q
35.0
m q
37.0
m q
m is the mass-to-charge ratio for a hydrogen ( 11 H ) nucleus. The data suggest that two isotopes are q
present with masses A.
17.5u and 18.5u.
B.
17.5u and 37.0u.
C.
18.5u and 5.0u.
D.
35.0u and 37.0u. (1)
29.
The half-life of a radioactive nuclide is 1×103 s. What is the probability of decay per second of a nucleus of the nuclide, quoted to one significant digit?
A.
7×10–4
B.
1×10–3
C.
1×103
D.
7×103 8
30.
A radioactive isotope has a half-life of five minutes. A particular nucleus of this isotope has not decayed within a time interval of five minutes. A correct statement about the next five minute interval is that this nucleus A.
has a lower than 50 chance of decaying.
B.
will certainly decay.
C.
has a 50 chance of decaying.
D.
has a better than 50 chance of decaying. (1)
31.
Which of the following correctly describes the nature of the energy spectra of alpha (), beta (), and gamma () radiation?
