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IBPhysicsSLExam QuestionsNuclear & Quantum PhysicsFusion & Stars

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First teaching 2023

First exams 2025

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Fusion & Stars (SL IB Physics)

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1
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A nuclide of deuterium H presubscript 1 presuperscript 2 and a nuclide of tritium H presubscript 1 presuperscript 3 undergo nuclear fusion.

Which statement is not correct about nuclear fusion?

  • For fusion to occur both nuclei must have high kinetic energy 

  • The process of fusion absorbs energy 

  • Fusion is the combining of two smaller nuclei into a larger nucleus

  • Fusion is the process that powers stars

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2
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Which row shows the conditions required for fusion to be sustained in the core of a star?

 

Density

Temperature

A.

 moderate very high

B.

 moderate moderate

C.

 very high very high

D.

 very high moderate

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    3
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    The letters W, X, Y and Z represent stars at these positions on the diagram.

    fusion-and-stars-mcq-e-q3-ib-hl-physics

    Which of the following is part of a possible evolutionary path of a star?

    • W → Y

    • X → Y

    • Y → W

    • Y → Z

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    4
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    Which of the following describes the sequence for the evolution of a star of about 10 solar masses?

    • nebula → supernova → protostar → main sequence star → red supergiant → neutron star

    • nebula → planetary nebula → main sequence star → red giant → supernova → white dwarf

    • nebula → protostar → main sequence star → red giant  → planetary nebula → white dwarf

    • nebula → protostar → main sequence star → red supergiant → supernova → neutron star

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    5
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    Astronomers measure the parallax angle of two nearby stars. The parallax angle of star X is 3.9 × 10−6 rad and the parallax angle of star Y is 1.6 × 10−7 rad.

    What can be deduced about the relative distances of the two stars from these measurements?

    • Star X is closer to Earth than Star Y.

    • Star Y is closer to Earth than Star X.

    • Star X and Star Y are both at a similar distance from Earth.

    • Nothing can be deduced from these measurements alone.

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    1
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    The following fusion reaction occurs in stars:

    straight H presubscript 1 presuperscript 2 plus straight H presubscript 1 presuperscript 3 rightwards arrow He presubscript 2 presuperscript 4 plus straight n presubscript 0 presuperscript 1

    The binding energies are given as follows:

    • The binding energy of deuterium, straight H presubscript 1 presuperscript 2 is 2.2 MeV
    • The binding energy of tritium, straight H presubscript 1 presuperscript 3 is 8.5 MeV
    • The binding energy of helium, He presubscript 2 presuperscript 4 is 7.1 MeV

    How much energy is released in this fusion process?

    • 2.2 MeV

    • 3.6 MeV

    • 7.1 MeV

    • 10.7 MeV

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    2
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    Five regions are labelled on the Hertzsprung-Russell diagram shown. 

    fusion-and-stars-mcq-m-q1

    Which sequence could show part of the evolution of a star like the Sun? 

    • 1 → 5 → 3 

    • 2 → 3 → 4 

    • 3 → 5 → 1 

    • 4 → 3 → 2 

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    3
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    Which of the following statements about stars in positions P, Q, R and S is correct?

    fusion-and-stars-ib-hl-physics

    • P and R have the same mass.

    • P has a lower surface temperature than S.

    • R is more massive than P.

    • R has a lower surface temperature than Q.

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    4
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    Tau Ceti is one of the closest stars to the Sun. Tau Ceti has a surface temperature of 5300 K and a luminosity of 0.55 LSun, where LSun is the luminosity of the Sun.

    Which of the following is the correct description of Tau Ceti?

    • main sequence star

    • red dwarf star

    • red giant star

    • white dwarf star

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    5
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    Betelgeuse is a red supergiant star with a surface temperature of T subscript B and a surface area of A subscript B.

    The Sun has a surface temperature of T subscript S and a surface area of A subscript S.

    Which pair of expressions are correct?

    • T subscript B space less than space T subscript S and A subscript B space less than space A subscript S

    • T subscript B space less than space T subscript S and A subscript B space greater than space A subscript S

    • T subscript B space greater than space T subscript S and A subscript B space less than space A subscript S

    • T subscript B space greater than space T subscript S and A subscript B space greater than space A subscript S

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    1
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    Fusion of hydrogen can be simply modelled within the Sun by using the following reaction:

    H presubscript 1 presuperscript 4 rightwards arrow scriptbase H e end scriptbase presubscript 2 presuperscript 4 plus 2 scriptbase e to the power of plus end scriptbase presubscript 1 presuperscript 0 plus 2 upsilon subscript e plus gamma presubscript 0 presuperscript 0

    This reaction releases about 30 MeV of energy.

    If the Sun has a power output of 3.9 × 1026 W, approximately how many of these fusion reactions are occurring every second?

    • 4 × 1020 s−1

    • 5 × 1026 s−1

    • 9 × 1033 s−1

    • 8 × 1037 s−1

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    2
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    Two stars, P and Q, have approximately the same radius. The surface temperature of star P is twice the surface temperature of star Q.

    Star P has a luminosity L subscript straight P and star Q has a luminosity L subscript straight Q.

    The ratio L subscript straight p over L subscript straight Q is approximately

    • 2

    • 4

    • 8

    • 16

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    3
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    All objects shown on a Hertzsprung-Russell diagram emit electromagnetic radiation.

    8-2-5a-h-hr-diagram-temperature-luminosity-mcq-igcse

    Some statements about two objects R and S are:

    1. R emits radiation with a higher mean frequency than S
    2. The wavelength of the peak intensity of the radiation emitted by S is in the red region of the visible light spectrum
    3. S and R both emit radiation with the same intensity

    Which statement(s) about R and S is/are correct?

    • I only

    • II only

    • I and II

    • I, II and III

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    4
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    Sirius is the brightest star in the night sky and is one of the closest stars to Earth.

    α-Centauri is the closest star to Earth, but Sirius has a luminosity about 16 times greater than the luminosity of α-Centauri. Sirius is twice as far away from the Earth as α-Centauri.

    The intensity of light from Sirius is I subscript S and the intensity of light from α-Centauri is I subscript alpha.

    What is the value of I subscript S over I subscript alpha?

    • 1 fourth

    • 4

    • 8

    • 16

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