DP Physics (last assessment 2024)

Question 19N.3.SL.TZ0.10b(ii)

Date	November 2019	Marks available	[Maximum mark: 3]	Reference code	19N.3.SL.TZ0.10b(ii)
Level	SL	Paper	3	Time zone	TZ0
Command term	Determine	Question number	b(ii)	Adapted from	N/A

b(ii).

[Maximum mark: 3]

19N.3.SL.TZ0.10b(ii)

Eta Cassiopeiae A and B is a binary star system located in the constellation Cassiopeia.

The following data are available.

Apparent brightness of Eta Cassiopeiae A = 1.1 × 10^–9 Wm^–2
Apparent brightness of Eta Cassiopeiae B = 5.4 × 10^–11 Wm^–2
Luminosity of the Sun, $L_{⊙}$ = 3.8 × 10²⁶ W

(b(ii))

The surface temperature of Eta Cassiopeiae B is 4100 K. Determine the ratio $\frac{radius of the Eta Cassiopeiae A}{radius of the Eta Cassiopeiae B}$ .

[3]

Markscheme

«from b∝ L∝ R² T⁴»

realization that $R^{2} \propto \frac{b}{T^{4}}$ «for binary stars which are same distance away» ✔

$\frac{R_{A}}{R_{B}} = \sqrt{\frac{(\frac{1.1 \times 10^{- 9}}{5.4 \times 10^{- 11}})}{{(\frac{5900}{4100})}^{4}}}$ ✔

$\frac{R_{A}}{R_{B}} = 2.2$ ✔

NOTE: Award [2] for answer 0.46 from inverted ratio.

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Option D: Astrophysics

Option D: Astrophysics » Option D: Astrophysics (Core topics) » D.1 – Stellar quantities

Option D: Astrophysics » Option D: Astrophysics (Core topics)

Question 19N.3.SL.TZ0.10b(ii)

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