| Date | November 2015 | Marks available | 2 | Reference code | 15N.3.SL.TZ0.16 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 0 |
| Command term | Show that | Question number | 16 | Adapted from | N/A |
Question
This question is about cosmic microwave background (CMB) radiation.
One of Newton’s assumptions was that the universe is static. The peak intensity of the cosmic microwave background (CMB) radiation has a wavelength of 1.06 mm.
Show that this corresponds to a temperature around 3 K.
Suggest how the discovery of the CMB in the microwave region contradicts Newton’s assumption of the static universe.
Markscheme
\(T = \frac{{2.90 \times {{10}^{ - 3}}}}{{{\lambda _{\max }}}} = \frac{{2.90 \times {{10}^{ - 3}}}}{{1.06 \times {{10}^{ - 3}}}}\);
\( = 2.7{\text{ K}}\);
Must show 2 sig figs or more, as 3 K is given.
current low temperature observed is a result of expansion;
(expansion) has caused cooling from high temperatures;
Examiners report
Well done by candidates, weaker candidates did not write their ideas clearly enough in (a)(ii). Part (b) was also quite well done, but only better candidates mentioned uncertainty in measurement of distances to galaxies. At SL the calculation of the temperature of the CMB was successful for most candidates, however, relating it to Newton’s static universe polarised candidates into non-answers or correct answers.
Well done by candidates, weaker candidates did not write their ideas clearly enough in (a)(ii). Part (b) was also quite well done, but only better candidates mentioned uncertainty in measurement of distances to galaxies. At SL the calculation of the temperature of the CMB was successful for most candidates, however, relating it to Newton’s static universe polarised candidates into non-answers or correct answers.
