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This question is about radioactivity - Edexcel - GCSE Physics - Question 3 - 2021 - Paper 1
Question 3
This question is about radioactivity. (a) Alpha (α), beta (β) and gamma (γ) are three types of radioactive emissions. Which statement describes all of these radioac... show full transcript
Worked Solution & Example Answer:This question is about radioactivity - Edexcel - GCSE Physics - Question 3 - 2021 - Paper 1
Step 1
Which statement describes all of these radioactive emissions?
Answer
The correct statement for the types of radioactive emissions is that they are all emitted by unstable nuclei, fitting the description of option B. Therefore, alpha (α), beta (β), and gamma (γ) emissions are all ionising and emitted by unstable nuclei.
Step 2
Describe one similarity and one difference between the numbers of particles in one nucleus of fluorine-19 and one nucleus of a radioactive isotope of fluorine.
Answer
Similarity: Both fluorine-19 and any radioactive isotope of fluorine have the same number of protons, which is 9.
Difference: Fluorine-19 has 10 neutrons, while a radioactive isotope of fluorine may have a different number of neutrons, which could affect the stability of the nucleus.
Step 3
Explain why the new count is greater than 268.
Answer
The new count is greater than 268 because the aluminium sheet, which initially absorbed some beta radiation, has been removed. This allows more beta particles to reach the G-M tube, resulting in a higher count of detected ionising radiation.
Step 4
Step 5
Step 6
Calculate the number of radium-223 nuclei remaining in the source after a time of 33 days.
Answer
First, we note that 33 days equals three half-lives of radium-223. The initial number of nuclei is given as 1.7 × 10²³. After three half-lives, the remaining quantity can be calculated using the formula:
where:
- (for three half-lives)
Thus:
N = 1.7 imes 10^{23} imes (0.5)^3 = 1.7 imes 10^{23} imes rac{1}{8} = 2.125 imes 10^{22}
Therefore, approximately nuclei of radium-223 remain after 33 days.