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Anyone doing astrophysics edexcel option topic for physics? watch

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    if you do reply.
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    (Original post by Supreme One.)
    if you do reply.
    Yeah i am.
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    me too!
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    yeah dont you find that in all the past papaers some of the questions that come up arent even in the book or the syllabus.
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    (Original post by Supreme One.)
    if you do reply.
    I am.
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    (Original post by Supreme One.)
    yeah dont you find that in all the past papaers some of the questions that come up arent even in the book or the syllabus.
    Yeah, I know what you mean. Our teacher gave us copies of his own notes that he updates after every exam so they include answers to all questions that have come up. Even so, it doesn't help us much if a new one pops up on the 14th!
    Having looked at a few past papers it seems that there will definately be questions on
    wiens law
    stefans law
    helmzhold russell diagrams
    and probably a question asking for two reasons why telescopes in space are better than ones on the ground..........

    Good luck!
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    (Original post by JeremyG)
    helmzhold russell diagrams
    Hertzsprung-Russell.
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    yeah but stuff about radio telescopes keeps popping up and it aint even in the book. also for example one question they asked the size of a pixel in a CCD and a grain for photographic emulsion. how would anyone expect to know that. i cant even find it on the internet
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    i agree
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    Yeah I do, but out teacher taught us all that stuff. :s
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    Yeah. I really wish I'd taken Solid Materials or Med Physics.
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    i wanted particle physics
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    Me too, looks a lot more interesting. And looks like it goes nicely with Radioactivity.
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    i mean they always give the same type of question like either the life of red giants etc. then theres the h-r diagram. but then they always throw in a question you have nether seen or learnt before such as radio telescopes etc.
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    Well you're meant to learn that...

    Only visible light (wavelength 400-700 nm - 700 is red light) and radio waves (very long wavelength) pass through the atmosphere well. So terrestrial telescopes can be used to pick up these two types of radiation. However Infra Red, microwaves and others need to be picked up above the atmosphere

    Water and CO2 absorbs IR radiation (greenhouse gasses)
    Ozone absorbs UV radiation

    telescopes need to be highly placed (like on mountains) for 3 reasons:

    - less light pollution
    - less atmospheric absorbtion
    - less atmospheric refraction

    CCDs:

    - high linearity - charge sent is proportional to photons arriving
    - high QE - ~98% of photons arriving are recorded
    - large dynamic range - can record a wide range of wavelengths

    - expensive
    - must be cooled to avoid heat in the CCD sending "fake" signals
    - can only photograph small areas of sky

    Photographic emulsion:

    - low QE - about 4% photons arriving are recorded
    - non-rewritable - CCDs can refresh and record films
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    The stuff about photographic emulsions and grain and pixel size is in the syllabus, so you should have been taught about it.

    What kinda stuff do they ask about radio telescopes? You should have been taught about that stuff as well, as the syllabus says "the importance of different wavelengths of radiation as a means of discovering information about distant objects. Use of satellites such as Hubble telescope, IRAS and COBE."
 
 
 
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