Radioactive Emissions (OCR Gateway GCSE Physics: Combined Science)

Topic Questions

1a2 marks

A student does an experiment with radioactive materials.

He investigates how the activity of radiation changes with distance.
The radiation moves from the radioactive source to a detector.
He measures the counts per minute at the detector.

q24-paper4-specimen-ocr-gcse-physics

The table shows the results.

Distance between source and detector (cm)	Count rate (counts per minute)
10	1024
20	256
40	64
80	16

Describe, using these results, how the count rate changes as the detector is moved away from the source.

[2]

How did you do?

1b3 marks

The student takes two further readings at 160 and 320 cm.

He adds these further readings to his table.

Distance between source and detector (cm)	Count rate (counts per minute)
10	1024
20	256
40	64
80	16
160	6
320	0

As the distance is increased to 160 and 320 cm, the results do not follow the same pattern as the other results.

Predict what these last two results should have been and explain the anomalies in the last two results.

[3]

How did you do?

Did this page help you?

1a3 marks

Some isotopes of cobalt are radioactive.

The isotope cobalt‐60 (Co‐60) has the symbol:

{}_{27}^{60}{Co}

The isotope cobalt‐57 (Co‐57) has the symbol:

{}_{27}^{57}{Co}

State the number of protons in a nucleus of Co‐60.

Number of protons = .......................................................... [1]

ii)

Give one similarity and one difference between the nucleus of Co‐57 and the nucleus of Co‐60.

Similarity ............................................................................................

Difference ...........................................................................................

[2]

How did you do?

1b4 marks

A teacher measures the radiation emitted by Co‐60.

She uses this equipment:

q18b-paper2-oct-nov2020-ocr-gcse-physics

The teacher’s results are shown in Table 18.1.

	Count-rate (counts per minute)
Measurement 1	191
Measurement 2	224
Measurement 3	212

Table 18.1

Explain why the teacher’s three measurements are not the same.

[1]

ii)

Use the teacher’s results in Table 18.1 to calculate the mean count‐rate for Co‐60.

Count‐rate = ............................ counts per minute [2]

iii)

Co‐60 emits gamma radiation.

The teacher puts thin aluminium foil between Co‐60 and the detector.

State what happens to the count‐rate.

[1]

How did you do?

1c4 marks

Explain what is meant by the half‐life of a radioactive isotope.

[1]

ii)

The half‐life of Co‐60 is 5 years.

The count‐rate of a sample of Co‐60 is 160 counts per minute.

Calculate the count‐rate of the Co‐60 after 10 years.

Count‐rate = ............................ counts per minute [3]

How did you do?

Did this page help you?

3a1 mark

A radioactive isotope has a half-life of 6 hours.

50 g of the isotope are put in a container.

What mass of the isotope is left after 6 hours?

Mass = ................................ g [1]

How did you do?

3b9 marks

This is a graph showing the radiation emitted from samples of three different isotopes A, B and C.

q23b-paper2-june2098-ocr-gcse-physics

Which isotope, A, B or C, takes the longest time to decay?

[1]

Tick (✓) one box.

A	$□$
B	$□$
C	$□$

ii)

Two scientists discuss the isotopes in the graph.

Scientist 1

Scientist 2

‘I think isotope A is more hazardous than
B.

A has a higher activity than B.’

‘I think isotope B is more hazardous than
A.

B has a longer half-life than A.’

Do you agree with the views of scientist 1 and scientist 2?

Use the graph and ideas about radioactivity and half-life to explain your answer.

Scientist 1 ....................................................................................................................

Scientist 2 ....................................................................................................................

[4]

iii)

Scientist 1 wants to identify the type of radiation emitted by isotope A.

This is a list of equipment Scientist 1 has in his laboratory:

• radiation detector
• piece of thick lead
• piece of cardboard
• piece of aluminium.

Describe how Scientist 1 does the experiment and explain how they can work out the type of radiation emitted.

You may include a diagram in your answer.

[4]

How did you do?

3c4 marks

This is a diagram to show a nuclear fusion reaction:

q23c-paper2-june2098-ocr-gcse-physics

Explain why this is nuclear fusion.

[1]

ii)

It is difficult for nuclear fusion reactions to occur on Earth.

Explain why nuclear fusion reactions occur in the Sun.

[2]

iii)

What will happen to our Sun when it runs out of hydrogen?

[1]

How did you do?

3d1 mark

Some scientists say nuclear fission is renewable. Other scientists say it is non-renewable.

Suggest why the scientists disagree.

[1]

How did you do?

Did this page help you?

5a1 mark

A teacher demonstrates an experiment about radioactivity. He demonstrates how different types of radiation can be absorbed.

He puts different barriers between the source and the Geiger-Müller tube. He uses four different radioactive sources A, B, C and D.

q17-paper2-june2018-ocr-gcse-physics

Suggest two safety precautions that the teacher should use when demonstrating this experiment.

1 .............................................................................................................................

2 .............................................................................................................................

[2]

How did you do?

5b6 marks

The teacher chooses source A and uses the Geiger-Müller tube to measure the count rate (counts per minute) for different barriers. He repeats the experiment with source B, source C and then source D.

Look at his results.

Source	Count rate using different barriers
Source	Paper	Aluminium	Lead	No barrier
A	113	112	22	112
B	20	21	20	182
C	162	23	21	164
D	282	78	24	280

He also finds that the average count rate with no sources and no barriers is 20.

Which source A, B, C or D emits gamma radiation only?

Explain your answer.

Source ............... because ............................................

[2]

ii)

Which source A, B, C or D emits alpha radiation only?

Explain your answer.

Source ............... because ............................................

[2]

iii)

Which source A, B, C or D could emit both beta and gamma radiation?

Explain your answer.

Source ............... because ............................................

[2]

How did you do?

5c2 marks

The teacher notices that the count rate behind the lead barrier ranges from 20 to 24.

Give two reasons why there are a wide range of results around 22 counts per minute.

1. ............................................................................................................................
2. ............................................................................................................................

[2]

How did you do?

5d2 marks

The teacher decides to repeat the experiment.

This time he records the number of counts for a much longer time interval for each source.

Explain why this is an improvement to the experiment.

[2]

How did you do?

Did this page help you?

	Download	View
Medium
Hard

Source	Half-life (years)	Radiation emitted
Americium-241 (Am-241)	432	Alpha
Thorium-228 (Th-228)	2	Alpha

Conclusion 1:	I think the results are very inaccurate. The isotope stops being radioactive and then gets more radioactive again.
Conclusion 2:	I do not think the isotope has a half-life.

Time (minutes)	Activity (counts per minute)
0
10
20	84
30	64
40	52
50	40
60	32
70	25
80	20
90	16