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Question 19M.3.SL.TZ2.bi

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

The following data are available for the Cepheid variable δ-Cephei.

Peak luminosity = 7.70 × 1029 W

Distance from Earth = 273 pc

Peak wavelength of light = 4.29 × 10–7 m

Determine the peak apparent brightness of δ-Cephei as observed from Earth.

[2]

Markscheme

d = « 273 × 3.26 × 9.46 × 10 15 = » 8.42 × 10 18 «m»  ✔

b = « L 4 π d 2 = 7.70 × 10 29 4 π ( 8.42 × 10 18 ) 2 = » 8.6 × 10 − 10 «Wm–2»  ✔

 

Examiners report

Calculating the brightness of a star from its luminosity was an easy question for most candidates. But quite a few did not convert parsecs into metres especially at SL.

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