Web viewThe diagram below shows a circuit involving a photoelectric cell. When UV light is shone...

Nuclear / Atomic Review Questions

1. Which of the following gives the correct number of protons and neutrons in a nucleus of

carbon-14 ( C146 )?

Protons Neutrons

A. 8 6

B. 6 8

C. 14 6

D. 6 14

2. A freshly prepared sample contains 4.0 μg of iodine-131. After 24 days, 0.5 μg of iodine-131 remain. The best estimate of the half-life of iodine-131 is

A. 8 days.

B. 12 days.

C. 24 days.

D. 72 days.

3. Which of the following causes the greatest number of ionizations as it passes through 1 cm of air?(The total energy of the ionizing radiation is the same.)

A. An alpha particle

B. A beta particle

C. A gamma-ray

D. An X-ray

IB Questionbank Physics 1

4. This question is about nuclear physics.

(a) (i) Define binding energy of a nucleus.

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(ii) The mass of a nucleus of plutonium ( Pu23994 ) is 238.990396 u. Deduce that the

binding energy per nucleon for plutonium is 7.6 MeV.

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(b) The graph shows the variation with nucleon number A of the binding energy per nucleon.

Plutonium ( Pu23994 ) undergoes nuclear fission according to the reaction given below.

n BaSr n Pu 10

14656

9138

10

23994 x

(i) Calculate the number x of neutrons produced.

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(ii) Use the graph to estimate the energy released in this reaction.

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(c) Stable nuclei with a mass number greater than about 20, contain more neutrons than protons. By reference to the properties of the nuclear force and of the electrostatic force, suggest an explanation for this observation.

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5. This question is about the photoelectric effect.

In an experiment to investigate the photoelectric effect, light of frequency f is incident on the metal surface A, shown in the diagram below. A potential difference is applied between A and B. The photoelectric current is measured by a sensitive ammeter. (Note: the complete electrical circuit is not shown.)

When the frequency of the light is reduced to a certain value, the current measured by the ammeter becomes zero. Explain how Einstein’s photoelectric theory accounts for this observation.

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6. This question is about atomic spectra.

Diagram 1 shows some of the energy levels of the hydrogen atom. Diagram 2 is a representation of part of the emission spectrum of atomic hydrogen. The lines shown represent transitions involving the –3.40 eV level.

(a) Deduce that the energy of a photon of wavelength 658 nm is 1.89 eV.

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(b) (i) On diagram 1, draw an arrow to show the electron transition between energy levels that gives rise to the emission of a photon of wavelength 658 nm. Label this arrow with the letter A.

(1)

(ii) On diagram 1, draw arrows to show the electron transitions between energy levels that give rise to the emission of photons of wavelengths 488 nm, 435 nm and 411 nm.Label these arrows with the letters B, C and D.

(1)

(c) Explain why the lines in the emission spectrum of atomic hydrogen, shown in diagram 2, become closer together as the wavelength of the emitted photons decreases.

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7. This question is about radioactive decay.Iodine-124 (I-124) is an unstable radioisotope with


proton number 53. It undergoes beta plus decay to form an isotope of tellurium (Te).

(a) State the reaction for the decay of the I-124 nuclide.

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(b) The graph below shows how the activity of a sample of iodine-124 changes with time.

(i) State the half-life of iodine-124

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(ii) Calculate the activity of the sample at 21 days.

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(iii) A sample of an unknown radioisotope has a half-life twice that of iodine-124 and the same initial activity as the sample of iodine-124. On the axes opposite, draw a graph to show how the activity of the sample would change with time.Label this graph X.

(1)

(iv) A second sample of iodine-124 has half the initial activity as the original sample of iodine-124. On the axes opposite, draw a graph to show how the activity of this sample would change with time. Label this graph Y.

(1)(Total 8 marks)

8. The diagram below shows a circuit involving a photoelectric cell. When UV light is shone onto


the metal cathode, electrons are emitted establishing a photocurrent.

Which of the following changes could cause the photocurrent to stop?

A. Increasing the potential difference of the power supply.

B. Increasing the frequency of the UV light.

C. Increasing the intensity of the UV light.

D. Changing the metal surface to one with a smaller work function.

9. Electrons are accelerated from rest through a potential difference V. Their de Broglie wavelength is λ. The accelerating potential difference is increased to 2 V. Which of the following gives the new de Broglie wavelength?

A. 2λ

B. 2

C. 2

D. 2


10. Which of the following energy level diagrams best represents the kinetic energy EK of the “electron in a box” model, where an electron is confined to move in one dimension? The variable n is an integer (1, 2, 3, 4 etc.).

A.

B.

C.

D.


11. A proton is confined within a nucleus. What is the order of magnitude of the uncertainty in its momentum?

A. 10–30 Ns

B. 10–20 Ns

C. 10–10 Ns

D. 1 Ns

12. Different nuclides spontaneously undergo radioactive decay, emitting either α, β or γ radiation.Which of the following correctly identifies all the emissions that do not have discrete energies?

A. α

B. β

C. γ

D. α and γ

13. The half-life of a radioactive isotope is 10 days. What is the percentage of the sample remaining after 25 days?

A. 0 %

B. 18 %

C. 25 %

D. 40 %


14. This question is about quantum aspects of the electron.

The wavefunction ψ for an electron confined to move within a “box” of linear sizeL = 1.0 × 10–10 m, is a standing wave as shown.

(a) State what is meant by a wavefunction.

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(b) State the position near which this electron is most likely to be found.

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(c) Calculate the momentum of the electron.

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(d) The energy, in joules, of the electron in a hydrogen atom, is given by E = 2

181018.2n

where n is a positive integer. Calculate the wavelength of the photon emitted in a transition from the first excited state of hydrogen to the ground state.

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(e) The electron stays in the first excited state of hydrogen for a time of approximately∆t = 1.0 × 10–10 s.

(i) Determine the uncertainty in the energy of the electron in the first excited state.

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(ii) Suggest, with reference to your answer to (e)(i), why the photons emitted in transitions from the first excited state of hydrogen to the ground state will, in fact, have a small range of wavelengths.

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(f) Diagram 1 shows the three lowest energy levels for an electron in the hydrogen atom.

Using the energy axis on diagram 2, draw the three lowest energy levels for the electron in a box model. You do not have to put any numbers on the vertical axis.

(2)(Total 13 marks)


15. Which nucleons in a nucleus are involved in the Coulomb interaction and the strong short-range nuclear interaction?

Coulomb interaction Strong short-range interaction

A. protons protons, neutrons

B. protons neutrons

C. protons protons

D. protons, neutrons neutrons

16. Two samples of radioactive substances X and Y have the same initial activity. The half-life of X is T and the half-life of Y is 3T. After a time of 3T the ratio

Y substance ofactivity X substance ofactivity

is

A. 8.

B. 4.

C. 41

.

D. 81

.

17. The nuclear equation below is an example of the transmutation of mercury into gold.

Au Hg H 19779

19980

21 + X

The particle X is a

A. gamma-ray photon.

B. helium nucleus.

C. proton.

D. neutron.

18. This question is about unified atomic mass unit and a nuclear reaction.

(a) Define the term unified atomic mass unit.

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(b) The mass of a nucleus of rutherfordium-254 is 254.1001 u. Calculate the mass in GeV c–

2.

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(c) In 1919, Rutherford produced the first artificial nuclear transmutation by bombarding nitrogen with α-particles. The reaction is represented by the following equation.

α + O N 178

147 + X

(i) Identify X.

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(ii) The following data are available for the reaction.

Rest mass of α = 3.7428 GeV c–2

Rest mass of N147 = 13.0942 GeV c–2

Rest mass of O178 + X = 16.8383 GeV c–2

The initial kinetic energy of the α-particle is 7.68 MeV. Determine the sum of the kinetic energies of the oxygen nucleus and X. (Assume that the nitrogen nucleus is stationary.)

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(d) The reaction in (c) produces oxygen (O-17). Other isotopes of oxygen include O-19 which is radioactive with a half-life of 30 s.

(i) State what is meant by the term isotopes.

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(ii) Define the term radioactive half-life.

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(e) A nucleus of the isotope O-19 decays to a stable nucleus of fluorine. The half-life of O-19 is 30 s. At time t = 0, a sample of O-19 contains a large number N0 nuclei of O-19.

On the grid below, draw a graph to show the variation with time t of the number N of O-19 nuclei remaining in the sample. You should consider a time of t = 0 to t = 120 s.

(2)

19. This question is about the photoelectric effect.

(a) State what is meant by the photoelectric effect.

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(b) Light of frequency 8.7 × 1014 Hz is incident on the surface of a metal in a photocell.The surface area of the metal is 9.0 × 10–6 m2 and the intensity of the light is1.1 × 10–3 W m–2.

(i) Deduce that the maximum possible photoelectric current in the photocell is 2.7 nA.

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(ii) The maximum kinetic energy of photoelectrons released from the metal surface is 1.2 eV. Calculate the value of the work function of the metal.

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20. This question is about the de Broglie hypothesis.

(a) State the de Broglie hypothesis.

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(b) Determine the de Broglie wavelength of a proton that has been accelerated from rest through a potential difference of 1.2 kV.

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(c) Explain why a precise knowledge of the de Broglie wavelength of the proton implies that its position cannot be observed.

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(Total 6 marks)

21. This question is about radioactive decay.

Nitrogen-13 ( N137 ) is an isotope that is used in medical diagnosis. The decay constant of

nitrogen-13 is 1.2 × 10–3 s–1.

(a) (i) Define decay constant.

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(ii) A sample of nitrogen-13 has an initial activity of 800 Bq. The sample cannot be used for diagnostic purposes if its activity becomes less than 150 Bq. Determine the time it takes for the activity of the sample to fall to 150 Bq.

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(b) (i) Calculate the half-life of nitrogen-13

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(ii) Outline how the half-life of a sample of nitrogen-13 can be measured in a laboratory.

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(c) Nitrogen-13 undergoes β+ decay. Outline the experimental evidence that suggests another particle, the neutrino, is also emitted in the decay.

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(Total 9 marks)


22. In a fission reaction, the total mass and the total binding energy before the reaction are Mi and Ei respectively, where the binding energy is defined as a positive quantity. After the reaction the total mass is Mf and the total binding energy is Ef. Which of the following correctly compares the total masses and the total binding energies?

Total mass Total binding energy

A. Mf > Mi Ef < Ei

B. Mf > Mi Ef > Ei

C. Mf < Mi Ef < Ei

D. Mf < Mi Ef > Ei

23. An electron is confined to move in one dimension in a box of length L. Which of the following gives the momentum of the electron in its lowest energy state?

A. Lh

4

B. Lh

2

C. Lh

D. Lh2

24. The magnitude of the uncertainty in the position of a particle is equal to the de Broglie wavelength of the particle. Which of the following is the minimum uncertainty in the momentum p of the particle?

A. π4p

B. pπ4

C. ph

D. hp


25. Which of the following provides evidence for the quantization of nuclear energy levels?

I. Alpha particles have discrete values of kinetic energies

II. Gamma-ray photons have discrete energies

III. Atomic line emission spectra

A. I only

B. II only

C. I and II only

D. I, II and III


Web viewThe diagram below shows a circuit involving a photoelectric cell. When UV light is shone...

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