DP Physics (last assessment 2024)
Question 19M.3.SL.TZ2.aii
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.SL.TZ2.aii |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Explain | Question number | aii | Adapted from | N/A |
aii.
[Maximum mark: 2]
19M.3.SL.TZ2.aii
Explain how Cepheid variables are used to determine distances.
[2]
Markscheme
the «peak» luminosity/actual brightness depends on the period
OR
More luminous Cepheid variables have greater period✔
measurements of apparent brightness allow distance determination
OR
Mention of 
✔
OWTTE
Examiners report
Many candidates knew that if the luminosity of the Cepheid is known then the absolute brightness can be used to determine distance. But far fewer candidates could link luminosity with the period of the Cepheid star. Many seemed to think that the luminosity of all Cepheids is the same.
