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Question 19M.3.SL.TZ2.13ai

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.3.SL.TZ2.13ai
Level SL Paper 3 Time zone TZ2
Command term Outline Question number ai Adapted from N/A
ai.
[Maximum mark: 2]
19M.3.SL.TZ2.13ai
(ai)

Outline the processes that produce the change of luminosity with time of Cepheid variables.

[2]

Markscheme

Cepheid variables expand and contract

OR

Radius increases and decreases

OR

Surface area increases and decreases ✔

Surface temperature decreases then increases✔

Surface becomes transparent then opaque ✔

OWTTE

Do not reward ‘change in luminosity/brightness’ as this is given in the question.

Accept changes in reverse order

Examiners report

The expansion and contraction of Cepheid stars was commonly mentioned. Changes in surface temperature and opacity were less commonly mentioned. A common misconception seems to be that the variation of luminosity is due to a change of the rate of fusion. A few candidates left this question unanswered.

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