Date: __________________
Decay Law
1.
The graph of the activity A of a radioactive sample against time t is shown below.
A / MBq
4
3
2
1
0
t/s
10
20
30
40
50
Find
(a) the decay constant of the sample.
(b) the number of undecayed nuclei at t = 0.
(c) the number of undecayed nuclei at t = 75.
(3 marks)
(2 marks)
(2 marks)
2.
Xenon-133 (Xe-133) is a radioisotope used in lung and liver imaging. It has a half-life
of 126 hours and an atomic number of 54. Xenon-133 would undergo beta decay and
turn into caesium-133 (Cs-133).
(a) How many nucleons are there in a xenon-133 nucleus?
(1 mark)
(b) Write down the nuclear equation for the beta decay of xenon-133.
(2 marks)
(c) Find the decay constant of xenon-133 in s−1.
(2 marks)
(d) A sample of xenon-133 has an activity of 2 × 108 Bq. Calculate its activity after
240 hours.
(2 marks)
Date: __________________
Decay Law
1.
The graph of the activity A of a radioactive sample against time t is shown below.
A / MBq
4
3
2
1
0
t/s
10
20
30
40
50
Find
(a) the decay constant of the sample.
(b) the number of undecayed nuclei at t = 0.
(c) the number of undecayed nuclei at t = 75.
(3 marks)
(2 marks)
(2 marks)
2.
Xenon-133 (Xe-133) is a radioisotope used in lung and liver imaging. It has a half-life
of 126 hours and an atomic number of 54. Xenon-133 would undergo beta decay and
turn into caesium-133 (Cs-133).
(a) How many nucleons are there in a xenon-133 nucleus?
(1 mark)
(b) Write down the nuclear equation for the beta decay of xenon-133.
(2 marks)
(c) Find the decay constant of xenon-133 in s−1.
(2 marks)
(d) A sample of xenon-133 has an activity of 2 × 108 Bq. Calculate its activity after
240 hours.
(2 marks)