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Date May 2017 Marks available 2 Reference code 17M.3.SL.TZ2.12
Level Standard level Paper Paper 3 Time zone Time zone 2
Command term Determine Question number 12 Adapted from N/A

Question

A particular emission line in a distant galaxy shows a redshift z = 0.084.

The Hubble constant is H0 = 68 km s–1 Mpc–1.

Describe what is meant by the Big Bang model of the universe.

[2]
a.

State two features of the cosmic microwave background (CMB) radiation which are consistent with the Big Bang model.

[2]
b.

Determine the distance to the galaxy in Mpc.

[2]
c.i.

Describe how type Ia supernovae could be used to measure the distance to this galaxy.

[3]
c.ii.

Markscheme

theory in which all space/time/energy/matter were created at a point/singularity

at enormous temperature

with the volume of the universe increasing ever since or the universe expanding

 

OWTTE

[2 marks]

a.

CMB has a black-body spectrum

wavelength stretched by expansion

is highly isotropic/homogenous

but has minor anisotropies predicted by BB model

T «= 2.7 K» is close to predicted value

 

For MP4 and MP5 idea of “prediction” is needed

[2 marks]

b.

\(\frac{v}{c} = z \Rightarrow v = 0.084 \times 3 \times {10^5} = 2.52 \times {10^4}\) «km\(\,\)s–1»

\(d = \frac{v}{{{H_0}}} = \frac{{2.52 \times {{10}^4}}}{{68}} = 370.6 \approx 370\) «Mpc»

 

Allow ECF from MP1 to MP2.

[2 marks]

c.i.

type Ia have a known luminosity/are standard candles

measure apparent brightness

determine distance from d = \(\sqrt {\frac{L}{{4\pi b}}} \)

 

Must refer to type Ia. Do not accept other methods (parallax, Cepheids)

[3 marks]

c.ii.

Examiners report

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

Syllabus sections

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