The reason for these changes in the count rate is the fact that beta particles are tiny electrons from the nucleus that are light and move very fast. It can ionize other atoms, but gets slowed down every time it hits another atom until, eventually, it runs out of energy and stops. Therefore the received count rate decreases as a result of the beta particles losing energy when they collide with other atoms; and also the count rate decreases because the distance between the beta source and the detector increases.
From my graph, I can see that the second part of my prediction which is: (The count rate is INVERSLY PROPORTIONAL to distance) is wrong. If the count rate is inversely proportional to distance, then a graph of ‘count’ on the y axis and ‘distance’ on the x axis should be a straight line going through the origin, and not a curve (which was what I got on my graph).
On the other hand, the graph does support my first prediction which was that of: (The received count rate decreases as the distance between the source and the detector increases).
Evaluation
On the whole, I think that this investigation went quite well and I believe I carried it out to the best of my abilities in the conditions provided. My range of 9 distances was adequate to plot a graph which supports my prediction, but, the first three distances went up in 5’s, then after that, the rest started going up in 10’s. In other words, the distances didn’t follow the same scale. As a result of this, my graph was a little bit wobbly, but there weren’t any anomalies.
There is not a great difference between my first and second set of results, showing that they are reasonably accurate and reliable. During the experiment, I handled the beta particle carefully by using forceps to hold and pick it up.
Sources of error
- The measurement on the ruler wasn’t really accurate and readable.
- The distance used, didn’t follow a particular scale because it started off in 5’s than switched to 10’s.
- The experiment was done in background radiation, and this was wrong. It was wrong because gamma waves are present in the air, so the readings were not only of beta particles, but of both gamma and beta.
- The count for each distance was read twice, and this wasn’t quite consistent.
Possible improvements
- A more accurate and readable ruler should be used to measure the distance.
- A proper and fair scale should be used for distance, so that the experiment could be a fair one. The distances should either go up in only 5’s or go up in only 10’s.
- The experiment shouldn’t be done in background radiation, so the readings will be fair; consisting of only beta particles and not gamma also.
- The count for each distance should be read/noted at least three times, in order to produce a more accurate average.
Possible extensions
- Investigating higher and lower distances to see if the trend continues or if there are other limiting factors.
- Further research into Radioactivity to explain my results in more depth.
