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unofficial astrophysics exam?? watch

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    hi,

    just resat my astro - you guys are prob still in the exam, but how'd everyone find it? Think i got 90ish%, but it depends on how the examers interpret the english of my answers :rolleyes: - my englsih sucks!

    pk
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    Ive just done mine too(just astro like you). it started of really easy, then I saw the final part.
    I got it all right in the end, but I had to think about it for a while!

    I wasnt sure about the IRAS question? What did you put?
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    I'm so angry- teacher forgot to give me a paper and suddenly said 'Start' and I had to quickly ask for a paper, and she took so long getting one and giving it to me. And the worst thing is I need that minute to finish off the last question!!!! Wien's Law, I wrote the formula but didn't have time to do the calculation. Grr.
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    I thought that there was a lot there for the time allowed! I had to rush mine and only just got it finished but about 3/4 of my center didn't finish the last two questions!
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    (Original post by Scottus_Mus)
    I thought that there was a lot there for the time allowed! I had to rush mine and only just got it finished but about 3/4 of my center didn't finish the last two questions!
    i learnt my lesson of poor time management from last year, and wasted no time this year - hopefully i'll get those questions on CCD's right - only thing i'm worried on.
    > what reasons did you guys put down?

    i said Advantages of CCDS are
    1) can be reused
    2) more efficient - usees more incident light
    3) couldn't think of a lst one so said it is faster - more photos per session, but is sort of related to my second point so not sure about it

    disadvantage i put down was that smallest grain is smaller than smallest pixel, so CCD's not good for viewing distant galaxies.

    oh and the last two bits - what did you get for that?

    for delta lambda maz i got something like 9.46micro metres, or something like that...anyone else get that?

    i'm sort of worried about it now - need to do good in it badly, cos i know i'm gonna mess up phy 4 and the synoptic:eek:

    anyone think they are valid?
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    (Original post by SinghFello)
    Ive just done mine too(just astro like you). it started of really easy, then I saw the final part.
    I got it all right in the end, but I had to think about it for a while!

    I wasnt sure about the IRAS question? What did you put?
    can't remember that one - jog my memory - you doing edexcel normal?

    pk
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    (Original post by Phil23)
    i learnt my lesson of poor time management from last year, and wasted no time this year - hopefully i'll get those questions on CCD's right - only thing i'm worried on.
    > what reasons did you guys put down?

    Advantages:

    1. They are cheap and easy to replace
    2. They are more eficcinet (about 70%)
    3. They provide a more linear response and can detect very dim light

    Disadvantage:
    1. The grains are larger in CCDs so more grainy images are produced

    threw in an extra on the end too

    2.CCDs don't provide a permanant record wheras photographic emulsions do.
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    [QUOTE=Scottus_Mus]
    Advantages:
    3. They provide a more linear response and can detect very dim light
    QUOTE]

    wasn't even taught that one, lol

    so how'd you find the paper - think you did good?
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    (Original post by Phil23)
    (Original post by Scottus_Mus)
    Advantages:
    3. They provide a more linear response and can detect very dim light
    wasn't even taught that one, lol

    so how'd you find the paper - think you did good?
    I thought it was good part from the penultimate question. I wrote down the rearranged eqn, but I didn't have time to finish it; so i showed how to work it and labeled results T1 and T2 and said that their 4√T1 - 4√T2 ≈ 500K

    I dunno if I'll get any maks for that though
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    (Original post by Scottus_Mus)
    I thought it was good part from the penultimate question. I wrote down the rearranged eqn, but I didn't have time to finish it; so i showed how to work it and labeled results T1 and T2 and said that their 4√T1 - 4√T2 ≈ 500K

    I dunno if I'll get any maks for that though
    methods right - wrong values i think - i got =307K which i said was ~100K

    what you get for the last question?

    P.S. If any of you guys are resitting stuff - do it in January - too much pressure with A2's and all if you do resits in june too (i wouldd, but i had no option, lol- my school does everything in jan:mad: I'd also reccomend resitting stuff to try and get averages up to around 89%, cos that way you'll have some slack with your A2's, cos the synoptic is a killer!
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    I got a difference of 29nm i think for the last question
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    (Original post by Whatsername)
    I got a difference of 29nm i think for the last question
    what ws your value of T - i took delta T as being 307K
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    (Original post by Whatsername)
    I got a difference of 29nm i think for the last question
    cant be right can it? i thought you had to use lambda max . T = 2.898E-3?

    if you got lambda max as being 29 nm that'd imply your temp difference was 99931 K - which is nowhere near 300K, unless i'm misunderstanding the question
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    I got 328K for the change in temp.
    I cant remember the change in colour. I stupidly used the given 300K instead of my answer. I think I got about 99nm change in wavelengh. Which is about right change from yellow to orange.


    So no one knows about the IRAS 3 mark question???
    Something about taking pictures of the sky using infrared in IRAS instead of doing it on the ground.
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    Basically...If you take pictures outside earth's atomosphere there are no scattering and no wavelengths being absorbed by dust.
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    What I meant was my difference in temperatures was about 328K - and then you had to calculate the decrease in wavelengths, using wavelength x Temp = 2.898 x 10..
    My 2 wavelengths were like 5.00 x 10^-7, and the other 5.29..x 10^-7, so the decrease was about 0.30 x 10^-7 m .. (30nm i think?)
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    (Original post by Whatsername)
    What I meant was my difference in temperatures was about 328K - and then you had to calculate the decrease in wavelengths, using wavelength x Temp = 2.898 x 10..
    My 2 wavelengths were like 5.00 x 10^-7, and the other 5.29..x 10^-7, so the decrease was about 0.30 x 10^-7 m .. (30nm i think?)
    everyone is getting different answers:eek:
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    what did you get for the decrease in wavelength?
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    (Original post by SinghFello)
    So no one knows about the IRAS 3 mark question???
    Something about taking pictures of the sky using infrared in IRAS instead of doing it on the ground.
    the usual stuff - scattering, scope can pick wavelengths that would be absorbed by earths surface, etc.
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    (Original post by Whatsername)
    what did you get for the decrease in wavelength?
    using my value of 307K i got something like 9.4micro metres
 
 
 
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