Irradiation and contamination

Figure 6 is a diagram representing an atom.

Write the names of the particles X, Y and Z on the lines next to each letter in Figure 6.

The nucleus of a different atom emits a gamma ray.

What happens to the number of particles in the nucleus?

A teacher demonstrates a radioactivity experiment to a class of students.

The teacher places a radioactive source in front of a radiation detector.

State one safety precaution the teacher should take.

The teacher uses the detector to measure the activity of the source several times.

Figure 7 shows the results.

The teacher tells the class that radioactive decay is random.

State how the data in Figure 7 supports this statement.

Calculate the mean of the four measurements in Figure 7.

mean =_........ Bq

The teacher moves the radiation detector to different distances from the radioactive source.

The teacher determines the mean detector reading at each distance from the source.

The teacher plots the results on graph paper, as shown in Figure 8.

The source emits alpha radiation only.

Explain how the graph in Figure 8 shows that the source only emits alpha radiation.

Give a reason why the mean detector reading in Figure 8 does not fall to zero in this experiment.

Figure 7 shows a safety sign on the door of a laboratory where radioactive materials are used.

State one way that radioactivity can be dangerous to humans.

State one piece of equipment that can be used to measure radioactivity.

Alpha (α) radiation and ultraviolet (UV) radiation are ionising radiations.

Give two other ionising radiations.

A sample of a radioactive isotope has a mass of 520 g.

The half‑life of the radioactive isotope is 18 days.

Calculate the mass of the original radioactive isotope remaining after 18 days.

mass after 18 days_........ g

Calculate the mass of the original radioactive isotope remaining after 54 days.

mass after 54 days_........ g

This question is about radioactivity.

Alpha (α), beta (β) and gamma (γ) are three types of radioactive emissions.

Which statement describes all of these radioactive emissions?

Fluorine-19 is a stable isotope of the element fluorine.

The element fluorine also has several radioactive isotopes.

Describe one similarity and one difference between the numbers of particles in one nucleus of fluorine-19 and one nucleus of a radioactive isotope of fluorine.

similarity_........

Figure 10 shows a Geiger–Muller (G–M) tube attached to a counter. The G–M tube is used to measure the activity of a source of beta (β) radiation. There is an aluminium sheet between the beta source and the G–M tube. The counter is switched on and after 1 minute shows a count of 268.

The aluminium sheet is taken away. The counter is reset to zero and then switched on again. A new count is taken for 1 minute.

Explain why the new count is greater than 268.

The beta source is then also taken away. The counter is reset to zero and switched on again. A new count is taken for 1 minute.

Give a reason why there would now be a reading on the counter.

State the SI unit for the activity of a radioactive source.

*(d) Exposing people to radioactive sources can be dangerous.

Describe the dangers of exposure to radioactive sources and what can be done to protect hospital staff when they are working with radioactive sources.

Equations

Sometimes food can become contaminated with radioactive substances.

Describe the harmful effects of eating food contaminated with radioactive substances.

Gamma radiation can be used in food processing to irradiate food.

Explain why some food is irradiated with gamma radiation.

Gamma radiation is part of the electromagnetic spectrum.

When the nucleus of an atom emits a gamma ray, the number of protons in the nucleus and the number of neutrons in the nucleus do not change.

State how the nucleus does change when it emits a gamma ray.

*(d) Gamma radiation is produced by radioactive decay.

Alpha radiation and beta radiation are also produced by radioactive decay.

Compare the processes of alpha decay and beta decay.

Your answer should include what each radiation is and what effect each decay has on the original nucleus.

How many protons are in the nucleus of an atom of strontium‑90?

How many neutrons are in the nucleus of an atom of strontium‑90?

The half‑life of strontium‑90 is 29 years.

The table in Figure 4 gives some information about how the mass of a sample of strontium‑90 changes with time.

Complete the table in Figure 4.

A teacher sets up an experiment to show some students how far beta particles travel in air.

Figure 5 shows some of the equipment she uses.

State the scientific name for the radioactivity detector shown in Figure 5.

The teacher also has:

• a radioactive source that emits only beta particles

• a metre rule.

State two precautions the teacher must take to protect herself from the effects of radioactivity.

Describe how the teacher could show how far beta particles travel in air.