SpaceEdexcel A-Level Physics: Topic test

20 questions, 54 marks

Edexcel A-Level Physics

Space topic test

Total 54 marks

Name

Class

Date

1
A red supergiant star has a luminosity of 1.6 × 10³¹ W. Observers on a planet orbiting another star are 4.0 × 10¹⁸ m from it.
(a)
What is the intensity of the light from the supergiant at the observers' position?
[1 mark]
A3.2 × 10⁻⁷ W m⁻²
B1.0 × 10⁻⁶ W m⁻²
C8.0 × 10⁻⁸ W m⁻²
D1.0 × 10¹² W m⁻²
(b)
A second star has the same luminosity, but the intensity received from it is 9 times smaller than from the supergiant. How does the distance to the second star compare with the distance to the supergiant?
[1 mark]
A3 times greater
B9 times greater
C81 times greater
D3 times smaller
(c)
Calculate the luminosity of the star as a multiple of the luminosity of the Sun, 3.85 × 10²⁶ W.
[2 marks]
Total for question 1: 4 marks
2
Astronomers add a nearby star, Kappa, to a catalogue. Its trigonometric parallax angle p, the angle subtended at the star by the radius of the Earth's orbit, is 2.4 × 10⁻⁶ rad. The radius of the Earth's orbit is 1.50 × 10¹¹ m.
(a)
Which is the distance from the Earth to Kappa?
[1 mark]
A3.6 × 10⁵ m
B3.1 × 10¹⁶ m
C4.2 × 10⁵ m
D6.3 × 10¹⁶ m
(b)
Which is the main reason that trigonometric parallax cannot be used to measure the distance to another galaxy?
[1 mark]
AThe light from a galaxy is too faint to be seen at all
BThe parallax angle is far too small to measure
CGalaxies move too quickly for their positions to be recorded
DParallax only works if the luminosity of the object is known
(c)
The intensity of the light from Kappa at the Earth is 3.0 × 10⁻⁹ W m⁻². Calculate the luminosity of Kappa.
[2 marks]
Total for question 2: 4 marks
3
A Cepheid variable star in a distant galaxy pulsates with a period that shows its luminosity is 1.2 × 10³⁰ W. The intensity of its light at the Earth is 3.5 × 10⁻¹⁵ W m⁻².
(a)
Calculate the distance from the Earth to the Cepheid variable.
[3 marks]
(b)
Explain why a Cepheid variable can be used to find distances much greater than those that can be found by parallax, and suggest why the distance calculated in (a) might be an overestimate.
[4 marks]
Total for question 3: 7 marks
4
Star P and star Q both have a surface temperature of 4000 K. P is a main-sequence star with a luminosity 0.10 times that of the Sun, found from its position on a Hertzsprung–Russell (HR) diagram. Q is a red giant with a luminosity 400 times that of the Sun. Both stars are at the same distance from the Earth.
(a)
Describe where P and Q are plotted on an HR diagram. Explain what has happened to produce Q and what will happen next to a star of mass similar to the Sun.
[6 marks]
(b)
The intensity of the light from P at the Earth is 2.0 × 10⁻¹⁰ W m⁻². The luminosity of the Sun is 3.85 × 10²⁶ W. Calculate the intensity of the light from Q at the Earth and the distance from the Earth to the two stars. Discuss how reliable this distance is.
[6 marks]
Total for question 4: 12 marks
5
In the laboratory, a calcium absorption line has a wavelength of 393.4 nm. In the light from a distant galaxy, the same line is observed at a wavelength of 397.3 nm. Take the speed of light as 3.00 × 10⁸ m s⁻¹.
(a)
What is the redshift z of the galaxy?
[1 mark]
A3.9
B9.9 × 10⁻³
C1.0 × 10²
D0.99
(b)
At what speed is the galaxy receding from the Earth?
[1 mark]
A3.0 × 10⁸ m s⁻¹
B3.0 × 10⁴ m s⁻¹
C3.0 × 10¹⁰ m s⁻¹
D3.0 × 10⁶ m s⁻¹
(c)
Use v = H₀d with H₀ = 2.2 × 10⁻¹⁸ s⁻¹ to calculate the distance to the galaxy.
[2 marks]
Total for question 5: 4 marks
6
A star in a binary system orbits the centre of mass of the pair. When its velocity is directly away from the Earth, its speed is 3.0 × 10⁴ m s⁻¹. A spectral line from the star has a frequency of 4.57 × 10¹⁴ Hz when the star is at rest relative to the Earth. Take the speed of light as 3.00 × 10⁸ m s⁻¹.
(a)
How does the frequency of the line observed at the Earth compare with 4.57 × 10¹⁴ Hz when the star is moving directly away from the Earth?
[1 mark]
AIt is lower, because the waves from the receding source are stretched
BIt is higher, because the source is moving
CIt is the same, because the speed of light is constant
DIt is zero, because the star is moving away
(b)
What is the magnitude of the change in the observed frequency?
[1 mark]
A4.6 × 10¹⁴ Hz
B4.6 × 10¹⁸ Hz
C4.6 × 10¹⁰ Hz
D4.6 × 10⁶ Hz
(c)
Half an orbit later the star is moving directly towards the Earth at 3.0 × 10⁴ m s⁻¹. Calculate the difference between the highest and the lowest frequencies observed. Ignore any motion of the whole binary system.
[2 marks]
Total for question 6: 4 marks
7
Hydrogen gas in a distant galaxy emits radio waves of frequency 1.420 GHz when at rest relative to the observer. Radio telescopes on Earth detect this emission from the galaxy at a frequency of 1.395 GHz. Take the speed of light as 3.00 × 10⁸ m s⁻¹ and the Hubble constant as 2.2 × 10⁻¹⁸ s⁻¹.
(a)
Calculate the redshift z of the galaxy and the speed at which it is receding from the Earth.
[3 marks]
(b)
Calculate the distance to the galaxy. Explain, in terms of wavefronts, why the observed frequency is lower than the emitted frequency, and state how the calculated distance would change if the true value of the Hubble constant were smaller.
[4 marks]
Total for question 7: 7 marks
8
A team of astronomers measures the Hubble constant using a galaxy that contains a standard candle of luminosity 3.0 × 10³⁵ W. The intensity of light from the standard candle at the Earth is 4.0 × 10⁻¹⁵ W m⁻², and the spectral lines from the galaxy show a redshift z = 0.018. A different team, using other methods, reports a noticeably lower value of the Hubble constant. Take c = 3.00 × 10⁸ m s⁻¹.
(a)
Explain how measurements of redshift and distance for many galaxies show that the universe is expanding, and why the disagreement between the two values of the Hubble constant leads to controversy about the age and fate of the universe.
[6 marks]
(b)
Calculate the Hubble constant from the data for this galaxy and hence estimate the age of the universe, assuming a constant rate of expansion. Evaluate whether this single galaxy is enough to give a reliable value.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).