nuclear physics questions

AS level Physics Nuclear & Particle Physics Questions

1. (a) (i) Describe, with the aid of a labelled diagram, the results of Rutherford’s alpha particle scattering experiment.

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(ii) Explain how these results reveal the structure of the atom.

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(b) Complete the diagram below to illustrate the paths of the alpha particles beyond the gold nucleus.

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Total 9 marks

Goldnucleus


2. The diagram below shows an alpha particle about to make a head on collision with a gold nucleus.

(a) If the alpha particle has an initial kinetic energy of 3.6 10 -21J, and a distance of closest approach to the gold nucleus of 10 -5m, calculate the number of protons in the gold nucleus. ( particle charge = 3.2 10 -19 C, proton charge = 1. 6 10 -19C, =8.910 -12Fm-1)

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(b) Sketch graphs on the axis below to show how the potential energy, kinetic energy and total energy of the alpha particle varies as it moves towards the gold nucleus. Label the graphs KE, PE, E respectively. No numerical labelling is required.

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(c) Determine the speed of the alpha particle when it is 10 -4m from the gold nucleus. (alpha particle mass = 6.4 10 -27kg)

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Total 12 marks

Goldnucleus

distance from gold nucleus

energy

10 -5m(closest approach)


3. (a) Draw a labelled diagram of the essential components of the apparatus used in Rutherford’s alpha particle scattering experiment.

[4]

(b) In this experiment the majority of alpha particles suffer no deflection, some are deflected through small angles and very few are strongly deflected. How do these results undermine J.J. Thompson’s plum pudding model of the atom?

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Total 7 marks


4. (a) Illustrate with labelled diagrams the models of the atom proposed by Rutherford and Thompson.

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(b) If the Thompson’s model were correct, describe, with the aid of a labelled diagram, the results that Rutherford would have observed in his classic alpha particle scattering experiment.

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Total 9 marks


5. The nuclear equation shown below represents the decay of uranium to thorium.

238 234 y

U Th + X + Q 92 90 z

(a) Determine the values of y and z

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(b) Identify the particle X

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(c) Q represents the energy released in this reaction. Which two forms does this energy take?

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(d) The thorium also decays by - emission forming an isotope of palladium (Pa). Write the nuclear equation for this decay.

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Total 7 marks


6. (a) Sketch a graph of binding energy per nucleon against mass number for nuclei of mass number up to 240.

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(b) Indicate on your graph the positions of the elements Hydrogen, Iron and Uranium.[3]

(c) Making reference to your graph, explain the terms nuclear fusion and nuclear fission.

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Total 9 marks

Bin

ding

ene

rgy

per

nucl

eon

Mass number 40 80 120 160 200 240 240


7. The nuclear equation shown below represents the decay of radium to radon with the release of energy.

226 222 4

Ra Rn + He + energy 88 86 2

In answering this question the following data may be usefulMasses: Ra 226 = 226.025u Rn 222 = 222.01761u

He4 = 4.002603u 1u = 1.661 10 -27kg Neutron = 1.008605u Proton = 1.007276u

c = 3.0 10 8ms –1

(a) Show, by appropriate calculations, that radon is more stable than radium.

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(b) Calculate the mass defect, in kg, for this reaction.

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(c) Calculate the energy released in this reaction.


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Total 9 marks


8. The diagram below illustrates the main components of a thermal reactor.

(a) Add appropriate labels to the boxes (i) to (vi)[6]

(b) Explain the purposes of the components labelled (iii) & (vi)

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(c) Suggest a suitable radioactive source for this reactor

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i)

ii)

iii)

iv)

v)

vi)


8. (d) Suggest two advantages and two disadvantages of the use of thermal nuclear reactors rather than fossil fuels to generate electricity.

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Total 15 marks


9. 238 235 U and U are radioactive isotopes of Uranium.

92 92

(a) State the correct terms, and meanings of, the 'top number' and 'bottom number'.

top number:.................................................................................................................................

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bottom number:..........................................................................................................................

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(b) Explain the meaning of the term 'isotope'.

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(c) Which of the two isotopes is the most stable? Justify your answer with relevant calculations.

Masses: U238 = 238.05082u U235 = 235.04394uNeutron = 1.008605u Proton = 1.007276u1u = 1.661 10 -27kg

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top number

bottom number


9. (d) Write down a balanced nuclear equation for the alpha decay of Ra to Rn

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Total 13 marks


10.(a) The binding energy per nucleon of a nucleus is determined from its mass defect and is a measure of the stability of the nucleus. Explain the meanings of the terms in bold.

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(b) This is the equation for a decay reaction of thorium:

228 224 4

Th Ra + He 90 88 2

Masses: Th238 = 228.02873u Ra 234 = 224.02020uHe4 = 4.002603u 1u = 1.66110 -27kg

c = 3.0 10 8ms-1

(i) Calculate the mass defect, in kg, for this the reaction.

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(ii) Calculate the energy released, in joules, for each disintegration of a thorium nucleus.

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(iii) Calculate the minimum mass of a thorium sample that could release 10000MJ of energy. (ignoring energy released by further decay processes)

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Total 11 marks

11.(a) A radioactive source is thought to emit alpha, beta and gamma radiation. With the aid of a labelled diagram, explain how this could be confirmed by an absorption experiment that can be carried out in a school laboratory.

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(b) List alpha, beta and gamma radiation, of similar energy, in ascending order of:

(i) Ionising ability (ion pairs created per mm in air)

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(ii) Range in air

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(iii)Mass

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(iv)Speed

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Total 10 marks 12. The diagram below (not to scale) illustrates the paths of beta minus and gamma radiation

through a uniform magnetic field.

(a) Label the paths in the diagram as either or radiation[1]

(b) Explain how you identified each type of radiation.

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(c)Add the path of an alpha particle, of similar energy, to the diagram[2]

(d)Sketch a diagram of the paths of the three types of radiation through the air in the absence of electric or magnetic fields

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3 cm


Total 8 marks


13. The half life of a sample of radioactive material is related to its decay constant by the equation:

T1/2 =

(a)Explain the meaning of the symbols:(i) T1/2

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(ii)

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(b)A sample of 24Na has a half-life of 234 hours.(i) Calculate the radioactive decay constant for 24Na

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(ii) How much time elapses before a 5g sample of pure radioactive 24Na contains 1g of undecayed 24Na atoms?

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(iii) How many disintegrations of 24Na occur in this time? (Avogadro’s number=6.02 1023)

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Total 10 marks

14.(a) Sketch a diagram of the apparatus that could be used in a school laboratory to determine the half-life of a radioactive sample. The sample is thought to emit radiation only, with a half-life of about one minute.

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(b) State the measurements that are required to accurately determine the half-life.

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(c) Explain how the measurements would be used to determine the half-life for the sample.

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14.(d) The following apparatus is used to measure radiation with a moving detector:

(i) The source is a gamma emitter with an initial activity of 1600Bq and a half-life of 5000s. The detector moves away from the source with a speed of 1ms-1. Sketch a graph of count rate against time for the first five seconds of the motion. Label the graph with three values of count rate.

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(ii) On the same axis sketch the graph that would have been obtained for a sample with a half-life of 1s. Label this graph B.

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Total 13 marks

Detector

1m initiallyco

unt r

ate/

Bq

time/s0 1 2 3 4 5

Movement

Source


15. The table below shows how the activity of a radioactive sample reduces with time.

Time / s Activity / s-1 ln (activity)0 100002 99124 98256 97388 964710 955012 940014 9350

(a) Complete the third column and plot the relevant straight-line graph that will allow you to determine the half-life of the sample.

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(b) Explain clearly how, and why, this graph can be used to determine half-life of the sample, given that A = A0 e -t.

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15. (c)Using the graph, calculate the decay constant and hence half-life of the sample.

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Total 11 marks


16. Here are two 'family trees' of some of the sub-nuclear particles:

(a) Fill in the blank boxes to show the other main types of particle and give examples in the lowest boxes.

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(b) According to Gell-Mann's theory, hadrons are made of more fundamental particles called quarks. Two types ('flavours') of quark are:

Quark Charge (e)up + 2/3

down - 1/3

Show how groups of three of these quarks can form:

(i) A proton

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(ii) A neutron

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Hadrons

proton

Kaon

electron


16.(c) Other hadrons are formed from two quarks. How is it possible for a particle made of two quarks to have a total charge of +1?

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(d) Name one other 'flavour' of quark.

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Total 11 marks


17. In reactions between sub-nuclear particles, various numbers have been found to be conserved(i.e. unchanged throughout a reaction).

(a) State whether or not the following numbers are conserved:

Number Conserved (Yes / No)BaryonMesonLepton

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(b) The following decay is observed to occur:

(i) State this equation in words:

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(ii) State three conservation laws that this decay demonstrates.

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(c) This reaction cannot occur:

Which conservation law does it break?

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Total 9 marks

p n + + + e

p + e n + e


18. Physicists are attempting to find a unified theory of the fundamental forces of nature.

(a)Name the four forces involved.

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(b)State the force involved in:(i) holding quarks together in a proton.

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(ii) decay of a proton.

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(iii) particle scattering by a nucleus.

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(c)These forces are described by the exchange of particles. Name two of the exchange particles involved in the situations listed in b).

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Total 9 marks


19. A bubble chamber is used to observe the tracks of particles formed by collision reactions. A researcher drew the following sketch from a bubble chamber photograph.

There is a magnetic field acting downwards into the plane of the diagram.

The reactions that took place were:

p n + + + e followed by: n p + - + e

(a)Label each of the tracks in the boxes on the sketch with the symbol of the particle it represents.

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(b)Explain why some of the particle tracks are shown as dashed lines.

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Total 8 marks

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nuclear physics questions

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