2022 · Specimen · 9702/04 | Q12

0/40parts marked · 0 of 77 marks

Question (12 of 12)7 marks · Practise this topic →

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Available practice: 77 of 100 marks. Parts 1(b), 4(b)(i), 4(c), 6(a)(ii), 6(b)(ii), 7(a)(i), 7(a)(ii), 9(b)(i), 9(c), 10(b)(ii) await marking support. Scores cover available parts only.

A star has a luminosity that is known to be 4.8 × 10²⁹ W. A scientist observing this star finds that the radiant flux intensity of light received on Earth from the star is 2.6 nW m⁻².

(a)(i)Name the term used to describe an astronomical object that has known luminosity.

Answer guidance

State A short answer. No explanation is needed, and adding one cannot earn extra marks.

[1 mark]

(a)(ii)Determine the distance of the star from Earth.

Answer guidance

Determine Work it out from what you are given or from the figure, and show how you got there.

[2 marks]

The Sun has a surface temperature of 5800 K. The wavelength λ_max of light for which the maximum rate of emission occurs from the Sun is 500 nm.

A scientist observing a star (luminosity 4.8 × 10²⁹ W) finds that the wavelength for which the maximum rate of emission occurs from the star is 430 nm.

(b)(i)Show that the surface temperature of the star is approximately 6700 K. Explain your reasoning.

Answer guidance

Explain Give reasons, not just what happens. Each distinct reason is usually worth a mark.

[2 marks]

A star has luminosity 4.8 × 10²⁹ W and, from Wien's displacement law, a surface temperature of approximately 6700 K.

(b)(ii)Use this information to determine the radius of the star.

Answer guidance

Using You must use the thing it names. An answer that reaches the right value another way may not score.

[2 marks]

9702/04/SP/22Cambridge International AS & A Level Physics 9702 · Specimen 2022 · Paper 4 · Question 12