0

5

10

15

20

25

30

35

0 50 100 150 200 250 300

Tim

e T

(s)

Activity (counts per second) A / Bq

Measuring the half life of Protactinium

The half life does not change with timebecause the amount of radio active decay always increases at the same rate. For example it you start with a Protactinium sample with 200 A/Bq, it would take 6 seconds for this amount to half, as you can see in the red lines. If you take another point like 50, the amount of time required to half it is also 6 seconds as shown with the gree n lines. As we can see the time taken for an amount to half is always the same which means that the halflife is constant, and for protactinium the half life is 6 seconds.

6 Seconds

6 Seconds

Investigating the half-life of Protactinium

Time / t (s) Average time for interval

0-10 5

12.5-22.5 17.5

25-35 30

37.5-47.5 42.5

50-60 55

62.5-72.5 67.5

75-85 80

87.5-97.5 92.5

100-110 105

112.5-122.5 117.5

125-135 130

137.5-147.5 142.5

150-160 155

162.5-172.5 167.5

180

192.5

205

217.5

230

242.5

255

267.5

To get the 10 seconds minus the background count I subtracted 6 counts from the amount of coutns in 10 seconds. Example: Counts per 10 seconds- 6 = Counts per 10 seconds minus the background counts.

Ex. 292-6 = 286

To get the activity I divided the amount of counts minus the background count by 10. Example: Counts per 10 seconds minus background count / 10 = Activity Ex. 286/10= 28,6

Graph is on page named graph

Half life= from 200 to 100 A/Bq the Protactinium took 6 seconds so the half life is 6 seconds.

Example: 200 A/Bq = 4 seconds, 100 A/Bq = 10, 10 - 4 = 6, so te half life of protactinium is 6 seconds

What to do: 1. Process your data by completing the table above. 2. Write example calculations in the space below for all the calculations you have to used in 1 above. 3. Use Excel to plot a graph of Activity (Y axis) against time (X axis) for Protactinium. Add a best fit logarithmic line to your data and show the equation on your graph. 4. Use the graph to find the half-life of Protactinium. 5. "The half-life of the radioactive sample does not change with time". Use your graph to provide evidence to support this state 6. Submit your work via Turnitin. 7. Present your completed work on your blog in a siutable format.

Background count rate 6 counts in 10 seconds

Counts in 10 seconds Counts per 10 seconds minus

background count

292 286

253 247

219 213

183 177

184 178

154 148

144 138

109 103

112 106

98 92

107 101

70 64

69 63

48 42

54 48

43 37

53 47

44 38

46 40

27 21

22 16

22 16

To get the 10 seconds minus the background count I subtracted 6 counts from the amount of coutns in 10 seconds. Example: Counts per 10 seconds- 6 = Counts per 10 seconds minus the background counts.

To get the activity I divided the amount of counts minus the background count by 10. Example: Counts per 10 seconds minus background count / 10 = Activity Ex. 286/10= 28,6

Example: 200 A/Bq = 4 seconds, 100 A/Bq = 10, 10 - 4 = 6, so te half life of protactinium is 6 seconds

2. Write example calculations in the space below for all the calculations you have to used in 1 above.

for Protactinium. Add a best fit logarithmic line to your data and show

life of the radioactive sample does not change with time". Use your graph to provide evidence to support this statement.

Activity (counts per second) A

/ Bq

28.6

24.7

21.3

17.7

17.8

14.8

13.8

10.3

10.6

9.2

10.1

6.4

6.3

4.2

4.8

3.7

4.7

3.8

4

2.1

1.6

1.6

To get the 10 seconds minus the background count I subtracted 6 counts from the amount of coutns in 10 seconds. Example: Counts per 10 seconds- 6 = Counts per 10 seconds minus the background counts.