Determine the penetrating power and the range in air of the three radioactive emissions (Plutonium 239 for alpha, Strontium 90 for beta and Cobalt 60 for gamma).

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To determine the penetrating power and the range in air of the three radioactive emissions (Plutonium 239 for alpha, Strontium 90 for beta and Cobalt 60 for gamma).

Method 1

The apparatus were set up as in the diagram below to measure the range in air up to 50 cm for each source.

Before the experiment took place the background radiation was measured as 80 counts in 5 minutes therefore 16 counts per minute.  Experimental precautions were:

The radioactive source is aligned with a ruler to the GM tube as accurately as possible so that the maximum radiation is measured

A set square was used to measure the exact point at which the source and tube were placed

The counter was reset each time so the counter read zero so this would reduce zero error in the experiment and the hold button was pressed to freeze the measurement

Thirty seconds were left between the start of the count and the recording so the reading would be less instantaneous and more reliable

Everything was kept constant for all three experiments and the counts were recorded at regular intervals of 5 cm.

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Safety precautions included removing the sources from a secure wooden box using thongs and tweezers and placed in plasticene, the set square was held using thongs and all those carrying out the experiment stood behind the source to minimise any direct radiation exposure.

Method 2

The equipment was set up as shown below to measure the penetrating power of each radioactive source.

Again the measurements were taken without the absorber to measure background radiation.  The source was placed quite close to the counter (1cm) and the thickness of the absorber ...

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Spelling and language are of a very high standard, but short, single point sentences with little punctuation such as commas are used throughout, which doesn’t present the good physics as well as it could. The graphs and tables are well presented and do help add to the information in the text. Appropriate scientific language and specifics is used well. The piece flows as the experiment is conducted - beginning, data collected, analysed and conclusion in order.

You have shown understanding of topics regarding your experiment, and used this to identify any problems or steps that must be taken to accurately conduct your experiment, such as testing the background radiation and removing this count from your result. You have chosen your radioactive materials well, but without information on why you chose these particular isotopes (which is a rich topic to talk about – really an opportunity missed there) this is irrelevant as it could be luck without evidence to the contrary. The last paragraph shows a 0.000% error in the results, which is incorrect, where it should be negligible and you should talk about this fact.

This is a well-structured and well thought out piece, with a good understanding of the underlying physics. You have included most necessary sections such as safety, method and evaluation, but you are missing your preliminary work. Even just a small paragraph stating your thoughts and choice of materials before the experiment would do, as you have not otherwise shown evidence of planning your experiment, so you could not achieve full marks. You have shown your raw data and shown the intermediate steps you have taken to determine your conclusion, which allows the reliability of your experiment to be analysed.