Cambridge IGCSE · Physics (0625)

Radioactivity: Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Radioactivity.

10 questions25 marksFree, no account

Question 1

1 mark

A student uses a pair of long tongs to handle a radioactive source.
Why is this procedure considered a valid safety precaution?

Question 2

1 mark

A nucleus of radium-226 (\( ^{226}_{88}\text{Ra} \)) undergoes alpha (α) decay to form a nucleus of radon (Rn).

How many neutrons are present in the resulting radon nucleus?

Question 3

1 mark

A student uses a detector to measure the count rate from a radioactive source. The background count rate is constant at \( 30 \text{ counts/minute} \).

At \( t = 0 \), the detector shows a total count rate of \( 510 \text{ counts/minute} \).
After \( 6.0 \text{ hours} \), the detector shows a total count rate of \( 90 \text{ counts/minute} \).

What is the half-life of this source?

Question 4

1 mark

Which of the following is a significant natural source of background radiation?

Question 5

1 mark

During beta (̒) decay, a change occurs within the nucleus of an atom. Which of the following describes this change?

Question 6

2 marks

State one specific source of background radiation that originates from food and drink and explain how it enters the human body.

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Question 7

4 marks

Explain why gamma (\(\gamma\)) radiation is significantly more penetrating than alpha (\(\alpha\)) radiation.

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Question 8

5 marks

A radioactive source is used to monitor the thickness of paper in a factory. Explain why a beta (\(\beta^-\)) emitter is more suitable for this application than an alpha (\(\alpha\)) or gamma (\(\gamma\)) source.

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Question 9

3 marks

A radioactive isotope has a half-life of \(8.0\text{ days}\). An initial sample of this isotope produces a count rate of \(640\text{ counts/s}\).

(a) Define the term half-life.
(b) Calculate the count rate of the sample after \(24\text{ days}\) have passed.
(c) State one safety precaution that should be taken when handling radioactive sources in a laboratory to reduce exposure.

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Question 10

6 marks

A student uses a Geiger-M0ller tube to measure the activity of a radioactive sample. The results are shown in the table below:

Time (min): 0, 15, 30, 45
Measured Count Rate (counts/s): 145, 85, 55, 40
Background Count Rate: 25 counts/s

(a) Calculate the corrected count rate at each time interval. (2)
(b) Use the corrected values to determine the half-life of the sample. (2)
(c) Explain why radioactive decay is described as random. (2)

Write your answer out first, then check it against the worked solution.

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