| Date | May 2015 | Marks available | 3 | Reference code | 15M.3.SL.TZ2.13 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | State | Question number | 13 | Adapted from | N/A |
Question
This question is about stars.
The Hertzsprung–Russell (HR) diagram shows the position of the Sun and three stars labelled A, B and C.
State the star type for A, B and C.
Determine the ratio \(\frac{{{\rm{radius of B}}}}{{{\rm{radius of A}}}}\)
The apparent brightness of C is 3.8 \( \times \) 10–10 Wm–2. The luminosity of the Sun is 3.9 \( \times \) 1026 W.
(i) State what is meant by apparent brightness and luminosity.
Apparent brightness:
Luminosity:
(ii) Determine the distance of C from Earth.
The graph shows the variation with wavelength λ of the intensity I of the radiation emitted by 1.0m2 of the surface of the Sun. The curve of the graph has been adjusted so that the maximum intensity is 1.
On the grid, draw a corresponding graph for star C. Your curve should have a maximum intensity of 1.
Markscheme
A: white dwarf;
B: main sequence / blue giant / blue supergiant;
C: red giant / red supergiant;
\(\frac{{{R_B}}}{{{R_A}}} = {10^3}\);
Award [2] for a bald correct answer.
(i) apparent brightness: (total) power received per unit area/per m2 } (accept luminosity for power)
luminosity: (total) power radiated;
Accept energy per second instead of power.
d=2.9 \( \times \) 1019 (m);
Award [1] for 2.9×1017 (misses factor of 10000).
Award [2] for a bald correct answer.
same shape as curve in graph and displaced to right;
peak at 10 ± 2 \( \times \) 10-7 m with intensity ≤1;
Examiners report
In part (a) nearly everyone could name the types of stars.
In (b) the ratio of star radii was usually correct, with the square root missed by many candidates.
The apparent brightness and power of a star in (c)(i) were usually correctly stated. Mistakes usually involved stating power per second or energy. Part (c)(ii) was done well also, although arithmetic errors were common. In (d) nearly all candidates found the star’s peak wavelength and drew a suitable graph. Overall a very well answered question.
In (d) nearly all candidates found the star’s peak wavelength and drew a suitable graph. Overall a very well answered question.
