DP Physics (last assessment 2024)

Question 18N.3.HL.TZ0.21

Date	November 2018	Marks available	[Maximum mark: 4]	Reference code	18N.3.HL.TZ0.21
Level	HL	Paper	3	Time zone	TZ0
Command term	Estimate, Show that	Question number	21	Adapted from	N/A

21.

[Maximum mark: 4]

18N.3.HL.TZ0.21

(a)

Show that the temperature of the universe is inversely proportional to the cosmic scale factor.

[3]

Markscheme

«wavelength of light/CBR» λ ∝ R ✔

reference to Wien’s law showing that λ ∝ $\frac{1}{T}$ ✔

combine to get result ✔

OWTTE

(b)

The present temperature of the cosmic microwave background (CMB) radiation is 3 K. Estimate the size of the universe relative to the present size of the universe when the temperature of the CMB was 300 K.

[1]

Markscheme

$\frac{{{R_{{\text{past}}}}}}{{{R_{{\text{now}}}}}} = \frac{3}{{300}} = 0.01$ ✔

Syllabus sections

Option D: Astrophysics

Option D: Astrophysics » Option D: Astrophysics (Additional higher level option topics) » D.5 – Further cosmology (HL only)

Option D: Astrophysics » Option D: Astrophysics (Additional higher level option topics)

Question 18N.3.HL.TZ0.21

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