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1 Name: Edexce Black Body Date: Time: Total marks available: Total marks achieved: Questions

2 Q1. A lamp consists of a filament in a vacuum. Under normal working conditions the filament has a temperature of 1600 K. A similar filament lamp that is gas-filled has a filament temperature of 3200 K. The ratio of the wavelength at which maximum intensity of radiation is emitted by the vacuum lamp to that for the gas-filled lamp is A 1:2 B 1:1 C 2:1 D 16:1 (Total for Question = 1 mark) Q2. Star A has twice the radius of star B but only half the surface temperature. The ratio of the luminosity of star A to luminosity of star B is A 1:4 B 1:2 C 2:1 D 4:1 (Total for question = 1 mark) Q3. A black body radiator of temperature T and surface area A has a luminosity L. Which of the following is the luminosity of a black body radiator with surface area A/2 and temperature 2T? (1)

3 (Total for question = 1 mark) Q4. A standard candle, within a nearby star cluster, is a distance D from the Earth. It produces a radiation flux F at the surface of the Earth. The flux at the surface of the Earth, for a standard candle of the same luminosity in a second star cluster, is 4F. The distance of the second star cluster from the Earth is (Total for question = 1 mark) Q5. If the surface temperature of the Sun were to double, the rate at which energy from the Sun is received on the Earth would increase by a factor of A 2 B 4 C 8

4 D 16 (Total for question = 1 mark) Q6. α-centauri is one of the nearest stars to our Sun. The surface temperatures of these two stars are about the same. α-centauri has a 20% greater diameter than the Sun. The ratio of the luminosity of α-centauri to the luminosity of the Sun is about A 1.2 B 1.4 C 1.7 D 2.1 (Total for Question = 1 mark) Q7. Rigel A in the constellation of Orion is one of the brightest stars in the sky. It is a massive blue variable star with an intensity peak at a wavelength λ max of 0.25 μm. On the axes below, sketch a graph of the intensity of radiation emitted by Rigel A against the wavelength of that radiation. (2)

Q8. Most stars lie on the main sequence. In the early 20th century, it was thought that the main sequence represented different evolutionary stages of stars.

5 Q8. Most stars lie on the main sequence. In the early 20th century, it was thought that the main sequence represented different evolutionary stages of stars. According to this model, stars form with a high temperature and luminosity and so are located in the top left of the main sequence. As stars radiated energy they would move down the main sequence over time. Scientists were unaware of fusion in the core of stars providing the energy for the star to shine. Using this obsolete model explain why, in the absence of fusion, the luminosity of the star would decrease over time. (3) Q9. A student is constructing a spreadsheet to calculate the radius R of some stars. To obtain the radius, the surface temperature T of the star must first be calculated. She is given values for the stars' luminosities L and the wavelengths λ max at which peak energy emission occurs. Part of the spreadsheet is shown, A is the surface area of the star. (a) Write an equation to show how the value in B2 is calculated. (1)

6 (b) Show that the value in D2 is about 0.2 (2) (c) The student was given the luminosity values to enter into column C. Describe how astronomers could determine the luminosity of a star. (2) (Total for Question = 5 marks) Q10. Betelgeuse is our greatest red giant. It has a luminosity of W and emits radiation with a peak energy emission occuring at wavelength of 850 nm. Show that Betelgeuse has a surface temperature of about 3000 K. Hence calculate the ratio of the radius of Betelgeuse, r B to the radius of the Sun, r s. r s = m (5)

7 r B /r s, =... (Total for question = 5 marks) Q11. In 2016 the Breakthrough Starshot initiative was announced. This project intends to send a fleet of small probes to Proxima Centauri, the nearest star to the Sun. This journey would take about twenty years. The radiation intensity at Earth from Proxima Centauri is W m 2. The luminosity of the Sun is (i) Show that the luminosity of Proxima Centauri is about distance to Proxima Centauri = m = W (ii) Proxima Centauri is described on a website as a main sequence star. Determine whether the surface temperature of Proxima Centauri is consistent with a position on the main sequence of the Hertzsprung-Russell diagram. radius of Proxima Centauri = m (3) (3)

8 (Total for question = 3 marks) Q12. (a) The Herzsprung-Russell (H-R) diagram is one of the most important tools in the study of stellar evolution. The H-R diagrams below are for a young star cluster and an old star cluster.

9 Use the diagrams to describe and explain how the old star cluster is different from the young star cluster. (b) Trigonometric parallax is one way in which stellar distances can be measured. Astronomers measure the parallax angle for two nearby stars. The parallax angle for star A is rad and that for star B is rad. (i) Without calculation, state what can be deduced from this data about the relative distances of the two stars. (6) (1)

(ii) The diagram shows the parallax angle for star A. Calculate the distance of star A from the Earth. 1 A.U. is 1.50 10 11 m (2) Distance =.

10 (ii) The diagram shows the parallax angle for star A. Calculate the distance of star A from the Earth. 1 A.U. is m (2) Distance =... (c) In addition to finding the distances to stars astronomers are interested in determining the temperatures of stars. The spectrum of star A is shown below. Use data from the graph to determine the surface temperature of star A. (3)

11 Powered by TCPDF ( Temperature =... (Total for question = 12 marks)

Earth-based parallax measurements have led to the conclusion that the Pleiades star cluster is about 435 light-years from Earth.

Earth-based parallax measurements have led to the conclusion that the Pleiades star cluster is about 435 light-years from Earth. 1 The Pleiades star cluster is a prominent sight in the night sky. All the stars in the cluster were formed from the same gas cloud. Hence the stars have nearly identical ages and compositions, but vary