Here are the results from the Protactinium Generator Experiment. Your task is to correct for background (take the background count per second away from the count rate) and then plot a graph of count rate (cps) against time (s). Remember the count rate was taken every 10 s but shows the value of the count rate (for one second)
Background count rate (c.p.m.) 48.0, 46.0, 42.0
Average background count rate (c.p.m.) 45.3
Average background per second (c.p.s.) work it out!
Time | Count rate |
---|---|
(s) | (cps) |
0 | 80.3 |
10 | 73.9 |
20 | 67.3 |
30 | 60.5 |
40 | 55.2 |
50 | 49.6 |
60 | 45.7 |
70 | 41.5 |
80 | 37.4 |
90 | 34.1 |
100 | 31.3 |
110 | 28.5 |
120 | 25.9 |
130 | 23.9 |
140 | 21.7 |
150 | 19.4 |
160 | 17.6 |
170 | 16 |
180 | 14.9 |
190 | 13.4 |
200 | 12.3 |
210 | 11.2 |
220 | 10.2 |
230 | 9.2 |
240 | 8.4 |
250 | 7.5 |
260 | 6.9 |
270 | 6.4 |
280 | 5.7 |
290 | 5.3 |
300 | 4.7 |
Indium 116 Half Life
Here are the results for the Indium-116 half life experiment. Warning, do not plot a graph in 15 minute intervals or you will have more difficulty finding the half life. Make the scale ten minute intervals.
You can track the experiment yourself through the link below
Background count = 31 c.p.m.
Time | Time from start | Count rate |
---|---|---|
(hours) | (mins) | (c.p.s.) |
9:00 | 0 | 675 |
9:15 | 15 | 570 |
9:30 | 30 | 452 |
9:45 | 45 | 375 |
10:00 | 60 | 328 |
10:15 | 75 | 275 |
10:30 | 90 | 219 |
10:45 | 105 | 181 |
11:00 | 120 | 164 |
11:15 | 135 | 149 |
11:30 | 150 | 126 |
11:45 | 165 | 106 |
12:00 | 180 | 90 |
Here are three more examples for you to practice producing a half life graph and for finding the half life of Protactinium
Example 1:
Background Count (cps): 5, 5, 3, 5, 4, 5, 5.
Time (s) | Count in 10s |
---|---|
0 | 308 |
10 | 279 |
20 | 240 |
30 | 217 |
40 | 197 |
50 | 182 |
60 | 165 |
70 | 158 |
80 | 145 |
90 | 129 |
100 | 116 |
110 | 109 |
120 | 98 |
130 | 89 |
140 | 80 |
150 | 75 |
160 | 66 |
170 | 60 |
180 | 55 |
190 | 50 |
200 | 46 |
210 | 43 |
220 | 35 |
Example 2:
Background Count (cps): 4, 3, 5.
Time (s) | Count in 10s |
---|---|
0 | 841 |
10 | 752 |
20 | 693 |
30 | 622 |
40 | 593 |
50 | 544 |
60 | 481 |
70 | 443 |
80 | 392 |
90 | 364 |
100 | 341 |
110 | 301 |
120 | 272 |
130 | 251 |
140 | 243 |
150 | 211 |
160 | 204 |
170 | 183 |
180 | 172 |
Example 3:
time (s) | Count in 10s | corrected count in 10s | Corrected Count Rate (cps) | Background count (cp10s) |
---|---|---|---|---|
0 | ||||
5 | 105 | 100.5 | 10.05 | 5 |
20 | 95 | 90.5 | 9.05 | 5 |
35 | 81 | 76.5 | 7.65 | 3 |
50 | 90 | 85.5 | 8.55 | 5 |
65 | 86 | 81.5 | 8.15 | 4.5 |
80 | 73 | 68.5 | 6.85 | |
95 | 76 | 71.5 | 7.15 | |
110 | 79 | 74.5 | 7.45 | |
125 | 53 | 48.5 | 4.85 | |
140 | 53 | 48.5 | 4.85 | |
155 | 58 | 53.5 | 5.35 | |
170 | 61 | 56.5 | 5.65 | |
185 | 60 | 55.5 | 5.55 | |
200 | 43 | 38.5 | 3.85 | |
215 | 60 | 55.5 | 5.55 | |
230 | 48 | 43.5 | 4.35 | |
245 | 45 | 40.5 | 4.05 | |
260 | 44 | 39.5 | 3.95 | |
275 | 42 | 37.5 | 3.75 | |
290 | 47 | 42.5 | 4.25 | |
305 | 28 | 23.5 | 2.35 | |
320 | 31 | 26.5 | 2.65 | |
335 | 36 | 31.5 | 3.15 | |
350 | 32 | 27.5 | 2.75 | |
365 | 24 | 19.5 | 1.95 |
You should now have had plenty of practice at finding the half life graphically, nothing should phase you now.