Seaweeds are of potential nutraceutical and medicinal values due to their wide range of constituents such as proteins, carbohydrates, fatty acids, peptides, minerals, vitamins, and hydrocolloids. However, the seaweeds accumulate toxic heavy metals fr
Radioactivity
MAY 2002
1
2
What is a beta-particle? A
a helium nucleus
B
a high-energy electron
C
four protons
D
two neutrons
The diagram shows a radioactivity experiment. counter
absorber
source
radiation detector
When a piece of paper is used as the absorber, the count rate drops to the background count rate. What radiation is the source emitting? A
alpha only
B
beta only
C
gamma only
D
alpha, beta and gamma
1
NOVEMBER 2002
3
A radioactive source emits radiation that can pass through a sheet of paper but not through thick aluminium. paper
thick aluminium
radiation no radiation passes through
all radiation passes through What does this show about the radiation?
4
A
It is alpha-particles.
B
It is beta-particles.
C
It is gamma-rays.
D
It is a mixture of alpha-particles and gamma-rays.
A sample of a radioactive isotope is decaying. Which atoms will decay first? A
impossible to know, because radioactive decay is random
B
impossible to know, unless the age of the material is known
C
atoms near the centre, because they are surrounded by more atoms
D
atoms near the surface, because the radiation can escape more easily
MAY 2003
5
Which type of radiation can be stopped by a sheet of paper? A
α-particles
B
β-particles
C
γ -rays
D
X-rays
2
6
The half-life of a radioactive substance is 5 hours. A sample is tested and found to contain 0.48 g of the substance. How much of the substance was present in the sample 20 hours before the sample was tested? A
0.03 g
B
0.12 g
C
1.92 g
D
7.68 g
NOVEMBER 2003
7
Which line in the table describes the nature of an -particle and a -ray?
-particle
8
-ray
A
helium nucleus
electromagnetic radiation
B
helium nucleus
electron
C
proton
electromagnetic radiation
D
proton
electron
A radioactive nucleus R decays with the emission of a -particle as shown. x yR
p → qS +
Which equation is correct? A
x=p
B
y=q
C
p=x–1
D
q=y–1
3
MAY 2004
9
10
Which line correctly describes α-particles?
electric charge
penetrates 1 cm of aluminium?
A
negative
yes
B
negative
no
C
positive
yes
D
positive
no
A small amount of a radioactive isotope contains 72 billion unstable nuclei. The half-life of the isotope is 4 hours. How many unstable nuclei would remain after 12 hours? A
6 billion
B
9 billion
C
18 billion
D
24 billion
NOVEMBER 2004
11
The equation shows the decay of the nuclide X. 226 88
X
→
P Q
What are the values of P and Q? P
Q
A
230
90
B
230
86
C
222
90
D
222
86
4
Y
+
4 2
α
12
During a fire in a laboratory storeroom, some radioactive material was spilled. A firefighter detected radiation through the lead-lined walls of the storeroom. The radiation was emitted by the radioactive material.
lead-lined storeroom
firefighter detector
radioactive material
Which type of radiation was being detected? A
α-particles
B
β-particles
C
γ-rays
D
X-rays
MAY 2005
13
14
Which type of radiation has the greatest ionising effect? A
α-particles
B
β-particles
C
γ-rays
D
all have the same ionising effect
A powder contains 400mg of a radioactive material that emits α-particles. The half-life of the material is 5 days. What mass of that material remains after 10 days? A
0 mg
B
40mg
C
100mg
5
D
200mg
NOVEMBER 2005
15
A radioactive source emits radiation that can pass through a sheet of paper but not through thick aluminium.
paper (all the radiation passes through)
thick aluminium (none of the radiation passes through)
radiation
What does this show about the radiation?
16
A
It is α-particles.
B
It is β-particles.
C
It is γ-rays.
D
It is a mixture of α-particles and γ-rays.
An unstable nucleus has 145 neutrons and 92 protons. It emits a β-particle. How many neutrons and protons does the nucleus have after emitting the β-particle? neutrons
protons
A
144
92
B
144
93
C
145
91
D
145
93
6
MAY 2006
17
The diagram shows five atoms in a radioactive substance. The atoms each give out an α-particle.
1st particle atom 1 atom 2
atom 5
atom 4
atom 3 2nd particle
Atom 1 is the first to give out a particle. Atom 3 is the second to give out a particle. Which atom will give out the next particle?
18
A
atom 2
B
atom 4
C
atom 5
D
impossible to tell
A Geiger counter detects radiation from radioactive sources. A radioactive source is inside a thick aluminium container as shown.
radioactive source
2m Geiger counter
thick aluminium container Which type of radiation from this source is being detected? A
α-particles
B
β-particles
C
γ-rays
D
radio waves 7
NOVEMBER 2006
19
20
Which line in the table describes the nature of an α-particle and of a γ-ray? α-particle
γ-ray
A
helium nucleus
electromagnetic radiation
B
helium nucleus
electron
C
proton
electromagnetic radiation
D
proton
electron
The count rates of four radioactive sources were measured at the same time on three consecutive days. Which source has a half-life of two days? Monday
Tuesday
Wednesday
A
100
50
25
B
200
140
100
C
300
300
300
D
400
200
100
MAY 2007
21
22
What are the most penetrating and the least penetrating types of radiation? most penetrating
least penetrating
A
α-particles
β-particles
B
β-particles
α-particles
C
γ-rays
α-particles
D
γ-rays
β-particles
The half-life of a radioactive substance is 5 hours. A sample is tested and found to contain 0.48 g of the substance. How much of the substance was present in the sample 20 hours before the sample was tested? A
0.03 g
B
0.12g
C
1.92g
8
D
7.68g
NOVEMBER 2007
23
A sheet of paper is placed between a radioactive source and a detector.
radioactive source
detector sheet of paper
Which types of radiation can pass through the paper?
24
A
α-particles and β-particles only
B
α-particles and γ-rays only
C
β-particles and γ-rays only
D
α-particles, β-particles and γ-rays
A sample of radioactive isotope is decaying. The nuclei of which atoms will decay first? A
impossible to know, because radioactive decay is random
B
impossible to know, unless the age of the material is known
C
atoms near the centre, because they are surrounded by more atoms
D
atoms near the surface, because the radiation can escape more easily
MAY 2008
25
What is a β-particle and from which part of a radioactive atom is it emitted? β-particle
emitted from
A
electron
nucleus
B
electron
outer orbits
C
helium nucleus
nucleus
D
helium nucleus
outer orbits
9
26
A sample of radioactive uranium has mass 1 g. Another sample of the same material has mass 2 g. Which property is the same for both samples? A
the amount of radiation emitted per second
B
the half-life
C
the number of uranium atoms
D
the volume
NOVEMBER 2008
27
The diagram shows an experiment to monitor the radiation from a radioactive gas. The counter readings are corrected for background radiation.
counter 000.0
radioactive gas
The table shows how the counter reading varies with time. time / seconds
0
20
40
60
80
100
120
140
160
180
counter reading / counts per minute
140
105
82
61
44
36
27
20
15
10
What is the half-life of the gas? A
between 20 and 40 seconds
B
between 40 and 60 seconds
C
between 60 and 140 seconds
D
between 140 and 180 seconds
10
28
Which material is commonly used as a lining for a box for storing radioactive samples? A
aluminium
B
copper
C
lead
D
uranium
MAY 2009
29
The graph shows the decay curve for one particular radioactive nuclide.
2500 count rate counts/min 2000
1500
1000
500
0 0
1
2
3
4
5 time/days
What is the half-life of this nuclide? A
1.0 day
B
1.5 days
C
2.0 days
11
D
2.5 days
30
A radioactive nucleus contains 138 neutrons. The nucleus emits an α-particle. How many neutrons are in the nucleus after it has emitted the α-particle? 134
A
B
136
C
138
D
139
NOVEMBER 2009
31
32
Which statement explains the meaning of the half-life of a radioactive substance? A
half the time taken for half the substance to decay
B
half the time taken for the substance to decay completely
C
the time taken for half the substance to decay
D
the time taken for the substance to decay completely
The diagram shows the paths of three different types of radiation, X, Y and Z.
X Y Z 2mm of plastic
10mm of aluminium
Which row in the table correctly identifies X, Y and Z? X
Y
Z
A
α-particles
β-particles
γ-rays
B
β-particles
α-particles
γ-rays
C
β-particles
γ-rays
α-particles
D
γ-rays
α-particles
β-particles
12
lead
MAY 2010
33
34
Which row describes the properties of α-particles? ionizing effect
radiation stopped by aluminium?
A
large
no
B
large
yes
C
small
no
D
small
yes
A radioactive substance has a half-life of 2 weeks. At the beginning of an investigation the substance emits 3000 β-particles per minute. How many β-particles will it emit per minute after 6 weeks? A
0
B
375
500
C
D
1500
NOVEMBER 2010
35
A radioactive element has a half-life of 70 s. The number of emissions per second, time.
N ,
of a sample of the element is measured at a certain
What was the number of emissions per second 70 s earlier? A
36
0
B
N / 2
C
N
D
2N
S is a radioactive source emitting α-particles, β-particles and γ-rays. A detector is placed 5 cm away from S. A thin sheet of paper is placed as shown in the diagram.
thin sheet of paper S
detector
5 cm Which radiations can be detected? A
α-particles and β-particles only
B
α-particles and γ-rays only
C
β-particles and γ-rays only
D
α-particles, β-particles and γ-rays 13
MAY 2011
37
38
Which row shows the relative ionising effects and penetrating abilities of α-particles and β-particles? ionising effect
penetrating ability
A
α greater than β
α greater than β
B
α greater than β
α less than β
C
α less than β
α greater than β
D
α less than β
α less than β
A powder contains 400mg of a radioactive material that emits α-particles. The half-life of the material is 5 days. What mass of that material remains after 10 days? 0 mg
A
B
40mg
C
100mg
D
200mg
NOVEMBER 2011
39
A scientist needs to use a source of γ-rays as safely as possible. Which action will
not
reduce the amount of radiation that reaches the scientist?
A
keeping the distance between the source and the scientist as large as possible
B
keeping the temperature of the source as low as possible
C
keeping the time for which the scientist uses the source as small as possible
D
placing a lead screen between the scientist and the source
14
40
The graph shows the activity of a radioactive source over a period of time. 2000 activity / counts per second 1500
