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Edexcel IGCSE Physics

Topic questions Space physics Red-shift & the expanding universe

Red-shift & the expanding universe

14 questions · 124 marks · about 2 hours

Red-shift and the expanding universe questions

TopicRed-shift & the expanding universe

Edexcel 4PH1 Red-shift and the expanding universe 14 questions

Physics Paper 2 June 2025 (R), Question 6 10 marks

This question is about cosmic microwave background radiation (CMBR) and the Big Bang.

(a)

CMBR has a mean frequency of 1.6 × 1011Hz.

(a)(i)

State the formula linking wave speed, frequency and wavelength.

[1]
Reveal mark scheme Mark scheme for question 6(a)(i)
(a)(ii)

Show that the mean wavelength of CMBR is about 2 mm.

[speed of light = 3.0 × 108m/s]

[3]
Reveal mark scheme Mark scheme for question 6(a)(ii)
(b)

CMBR was first released after the Big Bang.

When CMBR was first released it had a wavelength of about 9 × 10–5mm, but now it has a wavelength of about 2 mm.

Using this information, explain how CMBR supports the Big Bang theory.

[2]
Reveal mark scheme Mark scheme for question 6(b)
(c)

Explain how the cosmological red‑shift of galaxies also supports the Big Bang theory.

[4]
Reveal mark scheme Mark scheme for question 6(c)

Physics Paper 2 June 2025, Question 8 8 marks

This question is about cosmology.

(a)

Give two pieces of evidence that support the Big Bang theory.

[2]
Reveal mark scheme Mark scheme for question 8(a)
(b)

The galaxy NGC 300 is moving away from the Earth at a speed of 1.44 × 105m/s.

Hydrogen atoms in NGC 300 emit light with a reference wavelength of 4.3405 × 10−7m.

Calculate the wavelength of this light when it is detected at Earth.

Give your answer to five significant figures.

[speed of light in a vacuum, c = 3.00 × 108m/s]

[4]
Reveal mark scheme Mark scheme for question 8(b)
(c)

Another galaxy, Centaurus A, is much further away from the Earth than NGC 300.

Explain how the wavelength of light detected from hydrogen atoms in Centaurus A is different from the wavelength of light detected from hydrogen atoms in NGC 300.

[2]
Reveal mark scheme Mark scheme for question 8(c)

Physics Paper 2 November 2023, Question 8 5 marks

This question is about red‑shift.

(a)

The diagram shows two identical stars, A and B, orbiting each other.

Figure for question 8

Light from each star arrives at Earth.

As the stars move in their orbit, the wavelength of the light observed at Earth changes due to the Doppler effect.

Add an X to the diagram to show the position of star B when the light emitted from it shows maximum red-shift when detected on Earth.

[1]
Reveal mark scheme Mark scheme for question 8(a)
(b)

Light is received on Earth from a distant galaxy.

The longest wavelength of light arriving at Earth from the galaxy is 561 nm.

A lamp on Earth produces the same light with a wavelength of 550 nm.

Calculate the velocity of the galaxy.

[speed of light = 3.0 × 108m / s]

[4]
Reveal mark scheme Mark scheme for question 8(b)

Physics Paper 2 June 2023, Question 7 12 marks

(a)

A glass prism can be used to refract light.

Figure for question 7
(a)(i)

State the name of the piece of equipment used to measure angles.

[1]
(a)(ii)

Measure the angle of incidence and the angle of refraction for the light entering the prism.

angle of incidence =........ degrees

angle of refraction =........ degrees

[2]
Reveal mark scheme Mark scheme for question 7(a)(ii)
(a)(iii)

State the formula linking refractive index, angle of incidence and angle of refraction.

[1]
Reveal mark scheme Mark scheme for question 7(a)(iii)
(a)(iv)

Calculate the refractive index of the glass.

[2]
Reveal mark scheme Mark scheme for question 7(a)(iv)
(b)

Two galaxies, A and B, emit red light with a reference wavelength of 630 nm.

An astronomer measures the wavelength of red light from galaxy A when the light arrives at the Earth.

The astronomer’s value for the wavelength is 645 nm.

(b)(i)

Calculate the difference between the astronomer’s value for the wavelength and the reference wavelength of red light.

[1]
Reveal mark scheme Mark scheme for question 7(b)(i)
(b)(ii)

The change in wavelength happens because galaxy A is moving away from the Earth.

Calculate the speed of galaxy A.

[speed of light = 3.0 × 108m / s]

[3]
Reveal mark scheme Mark scheme for question 7(b)(ii)
(b)(iii)

Light from galaxy B has twice the redshift as light from galaxy A.

Galaxy B is twice as far away from Earth as galaxy A.

Explain how these observations support the Big Bang theory of the origin of the Universe.

[2]
Reveal mark scheme Mark scheme for question 7(b)(iii)

Physics Paper 2 June 2023 (R), Question 8 15 marks

This question is about stars.

(a)

The table gives some information about four stars.

StarMass in solar massesColourAbsolute magnitude
A0.7orange+7.5
B1.0yellow+4.8
C2.0blue+1.4
D17.1blue–16.8
(a)(i)

Star C is much more powerful than star A.

Stars A and C appear to have the same brightness when viewed from Earth.

Suggest how this is possible.

[1]
Reveal mark scheme Mark scheme for question 8(a)(i)
(a)(ii)

Using information from the table, explain which star is in the supernova stage of its evolution.

[3]
Reveal mark scheme Mark scheme for question 8(a)(ii)
(b)

Explain how a main sequence star evolves into a supernova.

[3]
Reveal mark scheme Mark scheme for question 8(b)
(c)

Astronomers have used supernovas in distant galaxies to investigate the expansion of the universe.

(c)(i)

Light emitted from a supernova at a wavelength of 7.774maths symbol10–7m was detected at Earth with a wavelength of 7.780maths symbol10–7m.

Calculate the speed at which the galaxy containing this supernova was moving away from the Earth.

[speed of light = 3.0maths symbol108m / s]

[4]
Reveal mark scheme Mark scheme for question 8(c)(i)
(c)(ii)

The astronomers investigated supernovas that showed a red-shift in the wavelengths detected in different galaxies.

The astronomers discovered that the red-shifted light detected from supernovas in nearby galaxies had shorter wavelengths than the red-shifted light detected from supernovas in galaxies further away.

Explain how this discovery supports the Big Bang theory.

[4]
Reveal mark scheme Mark scheme for question 8(c)(ii)

Physics Paper 2 January 2023 (R), Question 8 9 marks

Between 1929 and 1931, physicists Hubble and Humason investigated the red‑shift of light from galaxies at different distances from the Earth.

The distance unit they used is the megaparsec (Mpc).

(a)

Describe what is meant by the term red‑shift.

[2]
Reveal mark scheme Mark scheme for question 8(a)
(b)

The graph shows some of the results of their investigation.

Figure for question 8
(b)(i)

Draw a circle to show the anomalous data point.

[1]
Reveal mark scheme Mark scheme for question 8(b)(i)
(b)(ii)

Draw the line of best fit on the graph.

[1]
Reveal mark scheme Mark scheme for question 8(b)(ii)
(b)(iii)

The reference wavelength of the light used in this investigation is 660 nm.

Use information from the graph to determine the velocity of a galaxy at a distance of 0.75 Mpc.

[speed of light = 300 000 km/s]

[3]
Reveal mark scheme Mark scheme for question 8(b)(iii)
(b)(iv)

Explain why the graph from Hubble’s investigation provides evidence for the expansion of the universe.

[2]
Reveal mark scheme Mark scheme for question 8(b)(iv)

Physics Paper 2 January 2023, Question 8 9 marks

A binary star system has two nearby stars, which orbit each other in a circular path around a common centre of gravity.

Figure for question 8
(a)

In an eclipsing binary system, one star passes behind the other star in its orbit. This causes a decrease in the light intensity of the binary star system when viewed from Earth.

The graph shows how the light intensity of the binary star system changes with time.

Figure for question 8
(a)(i)

Suggest why the decreases in light intensity are not all the same.

[1]
Reveal mark scheme Mark scheme for question 8(a)(i)
(a)(ii)

Use the graph to determine the time period of the binary star system.

[1]
(a)(iii)

One of the stars in this binary system has an orbital speed of 19 km/s.

Calculate the orbital radius of this star.

[4]
Reveal mark scheme Mark scheme for question 8(a)(iii)
(b)

A different binary star system is in a distant galaxy.

When observed from the Earth, light from this galaxy has a longer wavelength than the wavelength of the light when it is emitted from the galaxy.

Explain why this gives evidence for the Big Bang theory.

[3]
Reveal mark scheme Mark scheme for question 8(b)

Physics Paper 2 January 2022 (R), Question 6 9 marks

(a)

State what is meant by the astronomical term galaxy.

[1]
Reveal mark scheme Mark scheme for question 6(a)
(b)

Which of these is a large collection of billions of galaxies?

Question 6, shown as an image
[1]
Reveal mark scheme Mark scheme for question 6(b)
(c)

Hydrogen is an element that can emit visible light waves.

The table shows the wavelength of one of these waves when detected from a laboratory sample of hydrogen and when detected from the hydrogen in two different galaxies.

The detected wavelengths from the galaxies are different from the detected wavelength from the laboratory sample because of the Doppler effect.

Wavelength in nm
Laboratory sample656.45
Galaxy A656.21
Galaxy B657.81
(c)(i)

Galaxy A and galaxy B are both moving relative to Earth.

Compare the motions of galaxy A and galaxy B relative to Earth.

[3]
Reveal mark scheme Mark scheme for question 6(c)(i)
(c)(ii)

Use data from the table to calculate the speed of galaxy B relative to Earth.

[speed of light, c = 3.0maths symbol108m/s]

[4]
Reveal mark scheme Mark scheme for question 6(c)(ii)

Physics Paper 2 January 2022, Question 8 7 marks

(a)(i)

A galaxy moves away from the Earth at a speed of 3.9 maths symbol 104km/s.

Question 8, shown as an image

Light from the galaxy is emitted with a wavelength of 6.2 maths symbol 10−7m.

Calculate the change in the wavelength of the light that is received by an observer on the Earth.

[3]
Reveal mark scheme Mark scheme for question 8(a)(i)
(a)(ii)

Calculate the wavelength of light that is received by an observer on the Earth.

[1]
Reveal mark scheme Mark scheme for question 8(a)(ii)
(b)

One of the pieces of evidence for the Big Bang theory is the red-shift of galaxies.

Explain how the red-shift of galaxies supports the Big Bang theory.

[3]
Reveal mark scheme Mark scheme for question 8(b)

Physics Paper 2 January 2021 (R), Question 6 6 marks

The Big Bang theory describes the evolution of the universe.

(a)

Explain how cosmic microwave background radiation (CMBR) supports the Big Bang theory.

[2]
Reveal mark scheme Mark scheme for question 6(a)
(b)

Hydrogen gas in a laboratory on Earth emits light with a wavelength of 605 nm.

A distant galaxy contains hydrogen which emits light of the same wavelength.

The wavelength of the light from the distant galaxy is measured as 683 nm on Earth.

Calculate the speed of the distant galaxy.

[speed of light = 3.0maths symbol108m/s]

[4]
Reveal mark scheme Mark scheme for question 6(b)

Physics Paper 2 November 2020, Question 5 6 marks

This question is about using radio waves to track an aeroplane.

aeroplane

Figure for question 5
(a)

Radio waves are emitted from an aerial at an airport, and are then reflected back to the aerial from an aeroplane.

The time taken between emitting the radio waves and receiving the waves back at the aerial is 1.9 milliseconds.

Show that the aeroplane is approximately 300 km away from the aerial.

[speed of radio waves maths symbol 3.0 × 105 km/s]

[3]
Reveal mark scheme Mark scheme for question 5(a)
(b)

As the aeroplane travels away from the airport, it sends a signal to the airport using radio waves with a wavelength of 1.2 m.

When the signal is received at the airport, the wavelength is 1.1 × 10-6 m longer than when it is emitted by the aeroplane.

Calculate the speed of the aeroplane using the formula

change of wavelength maths symbol speedof aeroplane wavelength
speedof radio wave

[speed of radio waves = 3.0 × 108 m/s]

[3]
Reveal mark scheme Mark scheme for question 5(b)

Physics Paper 2 November 2020 (R), Question 8 7 marks

The Big Bang theory suggests that the Universe is approximately 14 billion years old.

(a)

Describe the evolution of the Universe from the Big Bang until the present day.

[3]
Reveal mark scheme Mark scheme for question 8(a)
(b)

Describe the evidence that supports the Big Bang theory.

[4]
Reveal mark scheme Mark scheme for question 8(b)

Physics Paper 2 January 2020 (R), Question 8 15 marks

Also involves Hubble's law

Diagram 1 shows two identical buzzers connected with springs.

Figure for question 8

Spring A is connected to a post.

A force acts on the apparatus for a short period of time, pulling both buzzers to the right.

During this time, buzzer A moves 2 cm and buzzer B moves 4 cm.

(a)(i)

Explain why buzzer B travels with twice the average speed of buzzer A.

[2]
Reveal mark scheme Mark scheme for question 8(a)(i)
(a)(ii)

A student connects the microphone to an oscilloscope to measure the frequency of sound from the two buzzers while the force acts on the arrangement.

Explain the difference in the measured frequencies of sound from buzzer A compared to buzzer B.

[3]
Reveal mark scheme Mark scheme for question 8(a)(ii)
(b)

Diagram 2 shows an oscilloscope trace.

The trace represents the sound wave received by the microphone from buzzer A.

Figure for question 8

Measure the period of the sound waves from buzzer A.

Give your answer in standard form.

[3]
Reveal mark scheme Mark scheme for question 8(b)
(c)

Diagram 3 shows two distant galaxies and the Earth.

Figure for question 8

Light emitted from a nearby star has a wavelength of 590 nm.

The light from an identical star in galaxy P arrives at the Earth.

The wavelength of the light from the star in galaxy P is 600 nm.

(c)(i)

Calculate the change in wavelength for light from the star in galaxy P.

[1]
(c)(ii)

Galaxy Q is twice as far away from the Earth as galaxy P.

Suggest how the speed of galaxy Q relates to the speed of galaxy P.

[1]
(c)(iii)

Suggest a value for the change in wavelength of light from an identical star in galaxy Q when the light arrives at the Earth.

[1]
(c)(iv)

Explain how comparing the speeds of the two galaxies provides evidence for the Big Bang theory.

[4]
Reveal mark scheme Mark scheme for question 8(c)(iv)

Physics Paper 2 June 2019, Question 7 6 marks

(a)

Give two pieces of evidence for the Big Bang theory.

[2]
Reveal mark scheme Mark scheme for question 7(a)
(b)

Explain how this evidence supports the Big Bang theory.

[4]
Reveal mark scheme Mark scheme for question 7(b)

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