A LevelPhysicsOCRTopic Questions6. Particles & Medical Physics6.7 The Nuclear Atom

The Nuclear Atom (OCR A Level Physics)

Topic Questions

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1a4 marks
a)
In the 1800s, the atom was considered to be a fundamental particle. It was an indivisible particle of matter. Modern physics shows that this idea is not correct.

Describe the fundamental particles within an atom of carbon-14 (straight C presubscript 6 presuperscript 14).

In your answer state the composition of the hadrons.

[4]

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1b5 marks
b)
The half-life of the isotope carbon-14 is 5700 years (y).

i)
Show that the decay constant λ for this isotope is about 1.2 × 10−4 y−1.

[1]

ii)
Carbon-dating is a technique used to date an ancient wooden axe.

The ratio of carbon-14 to carbon-12 in the axe material is 78% of the current ratio of carbon-14 to carbon-12 in a living tree.

Calculate the age in years of the wooden axe.





age = ...................................... y [3]

iii)
State one assumption made in the calculation in (ii).

[1]

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1c6 marks
c*)
A graph of the density ρ of a nucleus against distance d from the centre of the nucleus is shown below.

q21c-paper-2-nov-2020-ocr-a-level-physics

The radius of the nucleus r is taken as the distance d where the density is half the maximum density.

Fig. 21.1 shows the density ρ variation for three different nuclei and Table 21.1 shows the nucleon number A of each nucleus.

q21c-2-paper-2-nov-2020-ocr-a-level-physics

Fig. 21.1

Nucleus Nucleon number A
Al-27 27
Mo-96 96
Hg-200 200

 
Table 21.1

Use the information provided opposite to
•    describe how the density of a nucleus depends on its nucleon number A
•    show numerically that r space proportional to space A to the power of 1 third end exponent
•    estimate the mean density of the nuclei.

[6]

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1a2 marks
a)
Describe the nature of the strong nuclear force.

[2]

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1b3 marks
b)
i)
Name a hadron found in the nucleus of an atom and state its quark combination.

name of hadron: .......................... quark combination: ..........................      [1]

ii)
Write a decay equation in terms of a quark model for beta-minus decay.

[2]

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1c2 marks
c)
The radius of a nucleus is directly proportional to Abegin mathsize 12px style begin inline style 1 third end style end style, where A is the nucleon number.
The mass of a proton and a neutron are similar.
Explain why the mean density of all nuclei is about the same.

[2]

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