ย
VIEW IN FULL SCREEN

# AQA GCSE Physics Radioactive decay

A nucleus is said to be stable if it has a certain amount of neutrons depending on the number of protons it has. If there are too many or too few neutrons, the nucleus is said to be unstable and will decay by emitting radiation. The same number of protons and neutrons are needed for nuclei of elements of fewer protons to be stable. The greater the number of protons, the more neutrons are needed for the nucleus to be stable. Radioactive decay occurs randomly and each decay is independent of the rest, therefore predictions about when an atom will decay cannot be made.

The decay constant, given by ฮป, is the probability of a given nucleus decaying per second. It is measured in sโปยน. It is calculated using the following formula: tโ/โ = ln2/ฮป, where tโ/โ is the half time of the isotope. The half time is defined as the time taken for the mass of an isotope to be halved or the time taken for its activity to be halved.

The activity of a radioactive object is the average number of radioactive decays per unit time and it is measured in becquerels (Bq). This can also be described as the rate of radioactive decay. The greater the time that has passed, the smaller the number of nuclei present, therefore the decay of the sample of the object will decrease. The number of decaying nuclei is directly proportional to the original number of them present.

The greater the time that has passed, the smaller the number of nuclei present, therefore the decay of the sample of the object will decrease. The number of decaying nuclei is directly proportional to the original number of them present. This can be expressed through the following formula: A = Aโexp(โฮปt), where Aโ is the initial activity and ฮป is the decay constant. Activity can also be calculated using the following formula: A = ฮปN, where N is the number of nuclei present.

Count rate is the number of decays recorded each second by a radiation detector. An example of a radiation detector is a Geiger-Muller tube. When radiation enters the GM tube, the counter clicks and the count is displayed on the screen. The count rate before the radioactive sample is brought into a room must be measured, since this constitutes for the background radiation. This must be subtracted from any readings of the count rate taken to account for background radiation.

# โ

What is the relationship between the number of protons a nucleus of an element has and the numbers of neutrons?

Did you know?

By simply logging in, you would be able to access 50% more questions.

# โ

Why does a Carbon nucleus require less neutrons than a Mercury one to be stable?

Did you know?

By simply logging in, you would be able to access 50% more questions.

# โ

Define the activity of a radioactive object.

Did you know?

By simply logging in, you would be able to access 50% more questions.

# โ

Given that the average number of radioactive decays per unit time for a radioactive sample is 1000, what is the activity of the sample?

Did you know?

By simply logging in, you would be able to access 50% more questions.

# โ

The activity of a radioactive sample is found to be 1800 Bq. What is the rate of radioactive decay of the sample?

Did you know?

By simply logging in, you would be able to access 50% more questions.

# โ

Give an example of a radiation detector.

Did you know?

By simply logging in, you would be able to access 50% more questions.

# โ

Label the given diagram for recording the count rate of a radioactive sample.

Did you know?

By simply logging in, you would be able to access 50% more questions.

# โ

Count rate must be corrected after it is recorded. Explain how it must be corrected.

Did you know?

By simply logging in, you would be able to access 50% more questions.

Have you found the questions useful?