Red-shift (AQA GCSE Physics)

Exam Questions

2 hours16 questions
1a3 marks

Define the Doppler effect.

1b2 marks

State the two properties which are observed to have changed due to the Doppler effect.

1c2 marks

An object is moving away from a stationary observer whilst emitting a steady sound wave.

 
 
(i)
State the property of the sound wave which increases.
[1 mark]
(ii)
State the property of the sound wave which decreases.
[1 mark]
(iii)
State the property of the sound wave which remains constant.
[1 mark]
1d7 marks

The following passage is about the Doppler effect and redshift.

Complete the following sentences by circling the correct words:

When a source starts to move away from / towards the observer, the wavelength of the wave broadens.

For sound waves, sound therefore appears at a higher / lower frequency to the observer.

For light waves, the light shifts towards the blue / red end of the electromagnetic spectrum due to its lower / higher frequency.

When a source starts to move away from / towards the observer, the wavelength of the wave shortens.

For sound waves, sound therefore appears at a higher / lower frequency to the observer.

For light waves, the light shifts towards the blue / red end of the electromagnetic spectrum due to its lower / higher frequency.

This is because blue / red light has a longer wavelength than blue / red light.

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2a3 marks
(i)
State the name of the theory that suggests that the Universe started with a massive explosion.
[1 mark]
(ii)
State the names of two observations that support this theory.
[2 marks]
2b3 marks

The table below contains statements about this theory.

Which of the following are correct?

Tick (✓) 3 boxes.

The universe began 14 million years ago square
There was a giant explosion known as the Big Bang square
This caused the universe to expand from a single point square
It heated as it expanded to form the universe today square
Each point in the universe expands away from the others square
So, the further away galaxies are the slower they are moving square
 
2c5 marks

The table below shows statements of evidence for the theory.

Place ticks (✔) in the correct boxes to indicate whether the statement is evidence from galactic redshift or CMB radiation.

 
Statement Evidence from Galactic Redshift Evidence from CMB Radiation
Astronomers discovered radiation in the microwave region of the electromagnetic spectrum coming from all directions    
Radiation is in the microwave region because the radiation initially from the big bang has redshifted as the Universe has expanded    
Observations of light spectrums from supernovae indicate that distant galaxies are receding    
Galaxies that are further away are moving faster, as their distance is proportional to their speed    
Light spectrums from distant galaxies show that light is redshifted which is evidence of the universe expanding    

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3a2 marks

Define redshift.

3b1 mark

Light from a distant galaxy appears to have been redshifted.

Which of the following rows correctly describes the change in the frequency and wavelength of the light when it is observed on Earth?

  Frequency Wavelength
A Decreases Decreases
B Increases Decreases
C Decreases Increases
D Increases Increases

    3c4 marks

    Figure 1 shows two people observing the same light source, which is in motion. The light is moving to the right.

    8-3-1c-e-redshift-labelling-light-bulb-sq-igcse

    Figure 1

    Complete the boxes on Figure 1 with words or phrases from the list below.

     
    higher frequency       lower frequency       phase difference       wavelength       blueshift       relative motion       star       redshift
    3d2 marks

    Which of the following are evidence for dark energy and dark matter?

    Tick (✓) 2 boxes.

       

    The rotation and motion of galaxies suggests that there is much more matter in the Universe than we are able to account for

    square

    Stars have nuclear fusion occurring at their core suggesting that most of the universe is comprised of hydrogen

    square

    Viewing distant supernovae suggests that the Universe is starting to expand at a faster rate

    square

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    4a1 mark

    Light from distant galaxies appears red-shifted to observers on Earth.

    Which of the following ideas does this provide evidence for?

        

    1. The Big Bang Theory

    2. The Universe is expanding

    3. Distant Galaxies are moving both towards us and away from us

    • 1 only

    • 1 and 2

    • 2 only

    • 1, 2 and 3

    4b4 marks

    This passage is about redshift.

    Complete the following sentences by filling in the correct words in the gaps. Use words from the box below:

     

    stretch out     slower     expanding     moving towards     

    receding     faster     black hole     doppler

     

    After the discovery of Doppler redshift, astronomers began to realise that almost all the galaxies in the universe are ........................ .

     
    This led to the idea that the universe must be ........................ .

     
    This caused the light waves to ..................... ..................... as they travel through space, shifting them towards the ........................ end of the spectrum.

     
    The more shifted the light from a galaxy is, the ........................ the galaxy is moving away from Earth.

    4c6 marks

    The following passage is about the start of the universe.

    Complete the passage using words in the box below.

     
    explosion        cold        expand        Big Bang        heats        hot        Big Crunch        shrinks        cools          faster

     

    Around 14 billion years ago, the Universe began from a very small region that was extremely ............... and dense.

    Then there was a giant explosion, which is known as the ............... ................

    This caused the universe to ............... from a single point to form the universe today.

    Each point expands away from the others and the universe ............... due to this.

    This is seen as galaxies move away from each other, and the further away they are the ............... they move.

    As a result of the initial ..............., the Universe continues to expand.

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    5a1 mark

    Which of the following statements provides evidence that the universe is expanding?

    • light from galaxies is red shifted

    • nuclear fusion occurs in stars

    • many stars have orbiting planets

    • stars form from large clouds of dust and gas

    5b1 mark

    An astronomer observes that light from a galaxy has been shifted towards the blue end of the spectrum.

    What can be deduced about the motion of the galaxy from this observation?

    • the galaxy is moving towards the Earth

    • the galaxy is moving away from the Earth

    • the galaxy is not moving relative to the Earth

    • the galaxy is expanding

    5c1 mark

    Figure 1 shows some wavelengths that were observed using light from a source in a laboratory:

    8-3-4c-e-hydrogen-spectrum-redshift-mcq-igcse

    Figure 1

    The same wavelengths of light observed from a distant galaxy were found to be redshifted.

    Which of the following statements about the redshifted light is correct?

    • all the lines move towards the 'short λ' side by different amounts

    • all the lines move towards the 'long λ' side by different amounts

    • all the lines move towards the 'short λ' side by the same amount

    • all the lines move towards the 'long λ' side by the same amount

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    1a1 mark

    What is the Universe?

    1b1 mark

    What name is given to the theory that the Universe started with a giant explosion?

    1c2 marks

    What are the main ideas of this theory?

    1d1 mark

    What is thought to be happening to the size of the Universe?

    1e2 marks

    State and explain briefly, one piece of scientific evidence which may be used to support this belief.

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    25 marks

    Explain, in as much detail as you can, the main scientific evidence supporting the big bang theory of the Universe.

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    3a1 mark

    Astronomers use special telescopes that can detect different types of electromagnetic waves to observe the Universe.

    Why is it important that we use the entire electromagnetic spectrum to study the Universe?

    3b1 mark

    What is meant by red-shift?

    3c1 mark

    In 2005 astronomers discovered a star with the biggest red-shift ever detected.

    What does this tell us about this star?

    3d2 marks

    The Big Bang theory is a theory about the origin of the Universe.

    Explain how the light arriving from distant galaxies provides important evidence in support of this theory.

    3e2 marks

    In 1998 some astronomers produced some evidence that suggested that some of the ideas scientists had about the Universe was incorrect.

    What should scientists do when a theory does not appear to be supported by new data?

    3f1 mark

    Although scientists have studied how the Universe was created, they do not know why the Universe was created.

    Suggest a reason why this question cannot be answered by scientists.

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    43 marks

    Binary stars are pairs of stars that both move around a common point.

    Figure 1 below shows one star in a binary system at two positions in its orbit.

    Figure 1

    fig-1-8-2-medium-aqa-gcse-physics

    The spectrum of light coming from the stars contains some dark lines known as absorption lines. The position of these lines in the spectrum is shown in Figure 2 for the two positions above, along with the same lines in the Sun’s spectrum.

    Figure 2

    fig-2-8-2-medium-aqa-gcse-physics

    These spectra provided important information about the movement of this star in the binary system.

    Explain how.

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    5a1 mark

    The light emitted from most galaxies is red-shifted relative to similar light observed on Earth.

    What does red-shift tell scientists about the direction most galaxies are moving?

    5b2 marks

    The size of this red-shift is different for different galaxies.

    What information about a galaxy can be found out by measuring the size of its red-shift?

    5c1 mark

    What do the above observations suggest is happening to the Universe?

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    6a1 mark

    The table in Figure 3 below shows the distance to several galaxies along with the speeds at which they are moving away from us.

    The final column shows the time for which the galaxies have been moving, which has been calculated using the formula:

    t i m e space equals space d i s tan c e space divided by space s p e e d

    Figure 3

    Galaxy

    Distance

    (in megaparsecs)

    Speed

    (in megaparsecs per billion years)

    Time

    (in billions of years)

    A 128 10 12.8
    B 325 25 13.0
    C 452 35  
    D 580 45 12.9
    E 806 63 12.8

    Complete the data for galaxy C.

    6b1 mark

    Describe the relationship between the speed of a galaxy and the distance the galaxy is from us.

    6c2 marks

    The data in the fourth column (time) provides evidence supporting the idea that the Universe was created in a big bang.

    Explain how.

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    1a3 marks

    Redshift can be used to determine whether a star is moving away from or towards the Earth. 

    State and explain what is meant by 'redshift' in this context.

    1b6 marks

    In a laboratory, hydrogen is found to emit light of wavelength 656.61 nm. The spectrum of a star observed on Earth is found to have the same line in the spectrum shifted to 656.68 nm.

    The following equation can be used to calculate the redshift:

    fraction numerator straight capital delta lambda over denominator lambda subscript 0 end fraction space equals space v over c

    Where:

    • increment lambda = change in observed wavelength
    • lambda subscript 0= wavelength observed in the laboratory
    • v = speed of the galaxy
    • c = speed of light = 3.0 × 108 m/s

    (i)
    Use the equation to calculate the speed of the star relative to the Earth.
    [4 marks]
     
    speed of the star = ................................... m/s
     
    (ii)
    Explain whether the star is moving towards or away from the Earth.
    [2 marks]
    1c4 marks

    A second spectral line is observed at 567.34 nm in the laboratory. 

    Determine the frequency of the spectral line from the star, as observed on Earth.

     
    Frequency = ......................................... Hz
    1d2 marks

    Explain the effect on the colour of light from the star if it were travelling towards the Earth.

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    2a
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    2 marks

    Define redshift.

    2b
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    3 marks

    The shift in wavelength can be identified using spectral lines in an absorption spectrum.

    The following absorption spectrum is generated using light from a source in a laboratory:

    iiyb8v8q_9-5-ib-hl-sqs-easy-q2c-question

    Sketch the spectrum obtained using light from a galaxy moving away from the Earth.

    2c
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    5 marks

    Redshift can be calculated using:

    fraction numerator straight capital delta lambda over denominator lambda end fraction equals fraction numerator straight capital delta f over denominator f end fraction equals v over c

    Where

    • lambda = wavelength
    • f = frequency
    • v = velocity of the galaxy
    • c = speed of light = 3.0 × 108 m/s

    An absorption line in the spectrum of light from a source in a lab in part (b) has a frequency of 5.783 × 1014 Hz. The same line in the spectrum of light from a distant galaxy has a frequency of 5.791 × 1014 Hz.

    Calculate the speed of the distant galaxy in relation to the Earth.

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    3a3 marks

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

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

    3b3 marks

    Describe the evidence for dark energy and dark matter.

    3c2 marks

    Describe the observations of distant galaxies compared to closer galaxies and discuss what this tells us about the universe.

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    4a2 marks

    In 1929, the astronomer Edwin Hubble noticed that the majority of galaxies in the Universe are moving away from us.

    The graph in Figure 1 shows some of the data that was collected by Hubble.

    8-2-h-4a-hubbles-constant-graph-aqa-gcse-physics-sq

    Describe the relationship between speed and distance shown by the best fit line in Figure 1.

    4b2 marks

    Hubble determined the speed of galaxies by measuring the red-shift of dark lines in the light being emitted by the galaxies.

    Explain how red-shift affects the wavelength and frequencies of these lines as observed from the Earth.

    4c4 marks

    The gradient of the best fit lines gives the value of an important quantity known as the Hubble Constant.

    Use the graph in Figure 1 to calculate a value for the Hubble constant.

    Show clearly how you obtained your answer.

    Hubble constant =................................ km/s per MPc

    4d2 marks

    Astronomers have continued to take measurements of the speeds and distances of galaxies, and have used these measurements to calculate more accurate values of the Hubble Constant.

    The graph in Figure 2 below shows some more recent data. 

    8-2-h-4d-hubbles-constant-graph-2

    Using Figures 1 and 2, explain why the value of the Hubble constant given by this more recent data can be considered to be more accurate than Hubble’s original value.

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    5a3 marks

    Figure 1 below shows the spectrum of light received on the Earth from the Sun and from a star in a distant galaxy.

    redshifted-spectrum

    Figure 1

    The spectrum contains some characteristic dark lines, which occur at very specific wavelengths in the laboratory.

    Explain how the shift in the position of the dark lines provides evidence to support the Big Bang theory.

    5b2 marks

    The data in Figure 1, along with data from other galaxies, can be used to plot a graph showing how the shift in position changes with the distance of each galaxy from the Earth, as shown in Figure 2.

    8-2-h-5b-hubble-graph-with-redshift-aqa-gcse-physics-sq

    A new galaxy is discovered with a red-shift of 0.02.

    Using the graph in Figure 2, estimate the distance to this new galaxy.

    Show clearly how you obtained your answer

    5c1 mark

    State an assumption you made in obtaining the answer to part (b).

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