AstrophysicsR - 1. SL and HL This was often well answered...

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1. SL and HL This was often well answered with many completely correct answers. However, a common error was to use the >, = and < symbols without explicitly relating them to ρ 0 and ρ . 2. HL only Quite a few candidates did not draw a straight line that went through the origin and a substantial number had difficulty with the calculation of the age of the universe, particularly with the units. 3. SL and HL This part was generally well done except that most candidates cited “expansion of the universe” without providing any evidence for it such as for example the redshifted light from distant galaxies. Again the answers lacked detail as for example in the definition of the cosmic background radiation. The part about the “universe expanding into a vacuum” was answered well by many who gave the standard Big Bang model answer. There was no evidence whatsoever that candidates who were familiar with string theories, M-branes, multiple universes etc through articles in scientific journals were, in any way, disadvantaged by this question. 4. HL only Most candidates answered this section correctly. There were amusing diagrams of the Milky Way galaxy! 5. SL and HL (a) There were many good complete answers. Some candidates lost marks because they merely made reference to ‘open’, ‘flat’ and ‘closed’, without explaining what these terms imply. (b) There were many very satisfactory answers for these calculations. Where ridiculous answers were obtained, these were accepted without comment by the candidates. 6. HL only (a) Although this should have been recall, there were few correct responses. Indeed, the regions marked frequently indicated that the candidates had little appreciation of the situation. 1
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(b) Very few candidates appreciated that light takes time to travel from the galaxy to Earth. Most attempted to attribute some special property to carbon to make it hotter than its environment. 7. HL only (a) With few exceptions, part (1) was completed successfully. In (ii), the Sun was frequently marked on the Main Sequence at too high a temperature. In (iii), the start and end points were usually correct but the path between the two was very varied. (b) Many answers included a description of stellar evolution. Most realised that the star would be expanding but few pointed out that there would be more power but over a much larger area. 8. HL only Many candidates were content to answer part (a) by returning the information given in the question. This approach did not gain any credit. Hubble’s law was generally well known but many candidates simply quoted the formula without defining any symbols. Part (b)(ii) asked for the experimental measurements required in order to determine the Hubble constant. A lot of
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AstrophysicsR - 1. SL and HL This was often well answered...

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