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Date May 2015 Marks available 3 Reference code 15M.3.HL.TZ1.5
Level Higher level Paper Paper 3 Time zone Time zone 1
Command term Explain Question number 5 Adapted from N/A

Question

This question is about Hubble’s law.

The light from distant galaxies is red-shifted. Explain how this red-shift arises.

[3]
a.

The graph shows the variation of recession speed with distance from Earth for some galactic clusters.

 

(i) Calculate, in s−1, the Hubble constant..

(ii) Estimate, in s, the age of the universe.

(iii) State the assumption that you made in your estimate in (b)(ii).

 

[4]
b.

Markscheme

(fabric of the) universe is expanding;
so the wavelength of the light increases;
during the time it has traveled from emitter to detector;

a.

(i) correct substitution into \({H_0} = \frac{v}{d}\);
2.7
×10-18 (s-1);

(ii) \(\frac{1}{{2.7 \times {{10}^{ - 18}}}} = 3.8 \times {10^{17}}\) (s)/3.7×1017;
Allow ECF from (b)(i).

(iii) universe has always had a constant rate of expansion;

b.

Examiners report

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

Syllabus sections

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