IBPhysicsHLTopic QuestionsNuclear & Quantum PhysicsFusion & Stars

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First teaching 2023

First exams 2025

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Fusion & Stars (HL 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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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?

  • 3.67 × 1020 reactions per second

  • 5.12 × 1026 reactions per second

  • 8.88 × 1033 reactions per second

  • 9.13 × 1037 reactions per second

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2
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The following nuclear fusion reaction is taking place in a nuclear reactor: 

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

The following data is available: 

  • The mass defect ≈ 0.02 u
  • Atomic mass unit, u ≈ 2.0 × 10−27 kg
  • Number of seconds in a year = 3 × 107

What is an estimate of the number of such fusion reactions required to keep an average household, which uses approximately 24 000 kWh of electrical energy per year, running for a year? 

  • 2 × 1015 

  • 1 × 1019 

  • 3 × 1021 

  • 2 × 1026 

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3
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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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4
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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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5
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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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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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