1.1. Which of these describes isotopes of an element?

1.2. Figure 9 represents a decay that can happen inside the nucleus of an atom.

Figure 9

Which decay is represented in Figure 9?

1.3. The half-life of cobalt-60 is 5 years.

A school cobalt source had an activity of 38.5 kBq in the year 2000.

Estimate the activity of this source in the year 2020.

activity = .............................................................. kBq

1.4. Explain what can happen to the body if a person has a prolonged exposure to gamma rays.

1.5. A G-M tube is connected to a counter.

A teacher places the G-M tube near to a radioactive source.

A student starts the counter and clock at the same time and writes down the readings shown on the counter every 15 s.

The student plots the readings with a line of best fit, as shown in Figure 10.

Figure 10

i) Calculate the average count rate, in counts/s, from the graph. Show your working on the graph.

average count rate = ...................................... counts/s[2]

ii) The student says that the experiment must have been done carelessly because the data seemed quite scattered away from the best fit line.

The teacher claims such results should be expected in radioactivity experiments.

Justify the teacher’s claim.

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