Exam code: 9PH0
Stars produce energy by nuclear fusion.
One particular fusion reaction between two protons () is shown below.
In this reaction 2.2 MeV of energy is released.
Only one of the particles shown in the reaction has binding energy.
Determine the binding energy per nucleon of this particle. Explain your answer.
Explain why high temperatures are necessary for fusion reactions to occur in stars.
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The graph below shows how the binding energy per nucleon varies with nucleon number.
Fission and fusion are two nuclear processes in which energy can be released.
(i) On the graph above, mark the element with the highest binding energy per nucleon.
(1)
(ii) Explain why nuclei that undergo fission are restricted to a different part of the graph than those that undergo fusion.
(2)
Explain, with reference to the graph in part (a), why the energy released per nucleon from fusion is greater than that from fission.
Explain how the binding energy of an oxygen nucleus can be calculated with information obtained from the graph in part (a).
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At the Culham Centre for Fusion Energy (CCFE) experiments are carried out to investigate nuclear fusion and the properties of plasmas. A plasma consists of ionised gas, containing positive ions and electrons.
In a fusion experiment at CCFE, ions of two isotopes of hydrogen fuse to produce helium ions and fast-moving neutrons.
Show that a single fusion reaction releases about 3 × 10−12 J of energy.
mass of = 2.013553 u
mass of = 3.015501 u
mass of = 4.001506 u
mass of = 1.008665 u
Fusion occurs naturally in the core of stars.
Explain why very high densities of matter and very high temperatures are needed to bring about and maintain nuclear fusion in stars.
In a plasma experiment 5.0 mg of deuterium, an isotope of hydrogen, occupies a volume of 98 m3. The temperature of deuterium is raised to 1.3 × 108 K. In this experiment, the deuterium behaves as an ideal gas.
i) Calculate the pressure due to the deuterium ions.
mass of deuterium ion = 3.3 × 10−27 kg
Pressure = .............................................(3)
ii) Calculate the root mean square speed of the deuterium ions at this temperature.
Root mean square speed = ......................................(2)
iii) The temperature of the plasma is monitored using the Doppler effect. Light from a laser is directed into the plasma and the wavelength of the light reflected is measured.
The Doppler shift observed when light is reflected by a deuterium ion is twice the Doppler shift that would be observed for a source of light moving at the same speed as the deuterium ion.
Calculate the maximum wavelength of light that would be detected after reflection from a deuterium ion moving at 1.5 × 106 m s−1.
wavelength of laser light = 1064 nm
Maximum wavelength detected = ..................................(3)
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The energy radiated by stars is released by nuclear fusion.
Explain the conditions required to bring about and maintain nuclear fusion in stars.
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