CAIE IGCSE Physics 5.2.4 Half Life Topic Practice

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Covered syllabus points

5.2.4.1—Half-life as the time for half the5.2.4.2—Half-life from data or decay curves5.2.4.3—Isotope choice using radiation type

Question 1

[Maximum number: 3]

A source contains a radioactive isotope of strontium. This isotope decays by emission of β\beta-particles. The half-life of this isotope is 29 years.

The initial mass of this isotope of strontium in the source is 25μ g25 \mu \mathrm{~g}.

Calculate the mass of the strontium isotope that decays in 87 years.

Question 2

[Maximum number: 4]

Only one isotope of gold occurs naturally on Earth.

There are several artificially produced isotopes of gold.

Gold-198 ( 79198Au{ }_{79}^{198} \mathrm{Au} ) is an artificial isotope which is used in medicine and in scientific research.
Gold-198 decays by β\beta (beta)-emission to a stable isotope of mercury.

Using Fig. 9.1, determine the half-life of gold-198.
half-life =

Question 3

[Maximum number: 2]

Leaks in underground water pipes are detected using radioactive tracers. Fig. 10.1 shows a radiation detector above a water pipe.

Fig. 10.1

Fig. 10.1

Question (a)

(a)

Explain why the radioactive isotope must not have a very short half-life.

[ 1 ]

Question (b)

(b)

Explain why the radioactive isotope must not have a very long half-life.
[Total: 9]

[ 1 ]
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