AQA GCSE Random Nature of Radioactive decay

AQA GCSE Random nature of radioactive decay

Random nature of radioactive decay

Radioactive decay is a random process, it cannot be predicted. 

It is not possible to predict when an individual nucleus will undergo decay. 

However, if you have a large number of nuclei, we can predict how many will decay in a certain time period. This is because we know that after a certain time period, the number of unstable nuclei will halve, due to the half life. 

If you take the example of the playing cards, you cannot easily draw an Ace of hearts. However, you do know that every 1 in 4 cards is a heart card. Therefore, if you go through the whole pack of 52 cards, 13 of them will be hearts and one will be the ace of hearts.

random playing cardsThink of radioactive decay being random a bit like selecting a playing card. The card you receive is random, radioactive decay is similar.

It is not possible to speed the process up, or slow it down. This makes radioactive decay different to a chemical reaction. 

Measuring the random nature of decay

The count rate detected by the GM tube varies continuously as shown by the graph. Sometimes the activity is higher and other times lower. 

Radioactive decay random nature experiment

 

In the case of the graph here, the count rate of the source was measured over a short period of time, just to show the random nature of decay.

If the source is measured over a longer period of time, it will slowly decay, so the activity would decrease, but it would still show random fluctuations in the activity level

Random nature of decay shown on a decay graph

 

 

Practice Questions

1.Explain why it is not possible to predict the count rate of a sample of radioactive isotope.

2. A student asked his teacher, if you heat a radioactive substance will it decay faster? Suggest the teacher’s response to the student’s question.

3. Which piece of apparatus can you use to measure the count rate of a radioactive substance?

 

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