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Date May 2018 Marks available 1 Reference code 18M.3.SL.TZ2.12
Level Standard level Paper Paper 3 Time zone Time zone 2
Command term Identify Question number 12 Adapted from N/A

Question

Data from distant galaxies are shown on the graph.

M18/4/PHYSI/SP3/ENG/TZ2/12

Estimate, using the data, the age of the universe. Give your answer in seconds.

[3]
a.

Identify the assumption that you made in your answer to (a).

[1]
b.

On the graph, one galaxy is labelled A. Determine the size of the universe, relative to its present size, when light from the galaxy labelled A was emitted.

[3]
c.

Markscheme

use of gradient or any coordinate pair to find H0 «= \(\frac{v}{d}\)» or \(\frac{1}{{{H_0}}}\) «= \(\frac{d}{v}\)»

convert Mpc to m and km to m «for example \(\frac{{82 \times {{10}^3}}}{{{{10}^6} \times 3.26 \times 9.46 \times {{10}^{15}}}}\)»

age of universe «= \(\frac{1}{{{H_0}}}\)» = 3.8 × 1017 «s»

 

 

Allow final answers between

3.7 × 1017 and 3.9 × 1017 «s» or 4 × 1017 «s»

[3 marks]

a.

non-accelerated/uniform rate of expansion

OR

H0 constant over time

 

OWTTE

[1 mark]

b.

z « = \(\frac{v}{c}\)» = \(\frac{{4.6 \times {{10}^4} \times {{10}^3}}}{{3.00 \times {{10}^8}}}\) = 0.15

\(\frac{R}{{{R_0}}}\) = «z + 1» = 1.15

 

\(\frac{{{R_0}}}{R}\) = «\(\frac{1}{{1.15}}\) =» 0.87

OR

87% of the present size

 

[3 marks]

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Option D: Astrophysics » Option D: Astrophysics (Core topics) » D.3 – Cosmology
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