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OCR Physics B G495 Field and Particle Pictures June 21st 2011 Exam Thread watch

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    (Original post by Unkempt_One)
    You forgot to multiply by 25 for the number of years.
    ahhh daymm! im sure it said something like about how the dose equivalent is over a life time so i just ignored the years cant really remember i assume your right tho coz thinking of it does sound wrong what did :/
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    Thanks dont think i can get a A*..

    For the very last question i wrote about how using the inferometer you can look for brightdark spots as you move the mirror, so you can do measurements to a resolution of half a wavelength. And v=f.lambda and all that to make it even more precise..

    Was just from what i was reading in the article though.
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    http://www.bbc.co.uk/news/education-13857911

    Was this us?
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    http://www.bbc.co.uk/news/education-13857911

    Was this us?
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    Why's everyone saying their people died? I'm pretty sure my 4 (4.35) people only had cancer
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    (Original post by Unkempt_One)
    The answer is 4.35, end of.
    Same here but I just wrote 4.35 should I write it as 4 instead?

    Not too bad, section a&b r nice but section c's a bit challenge for me, anyway better than the fp2 & 3 I did. Hopefully I can get an A finger crossed xxx

    tho i still got some careless mistakes Can anyone tell me about the phasors' and the air tube in section C ?? I can't get the mass of uranium in section B either ?
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    Just mentioned on BBC news that there was an unanswerable question on the paper - anyone got any idea what it was?
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    (Original post by wki)
    Same here but I just wrote 4.35 should I write it as 4 instead?

    Not too bad, section a&b r nice but section c's a bit challenge for me, anyway better than the fp2 & 3 I did. Hopefully I can get an A finger crossed xxx

    tho i still got some careless mistakes Can anyone tell me about the phasors' and the air tube in section C ?? I can't get the mass of uranium in section B either ?
    I also got 4.35
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    (Original post by Laurengemma7)
    Just mentioned on BBC news that there was an unanswerable question on the paper - anyone got any idea what it was?
    Wasnt this paper, OCR A
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    BBC: "An error in a question in the A-level physics paper, taken on Tuesday morning, used the wrong measurements." (OCR)

    Was this A or B?

    Edit, Cheers Alex.
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    I liked this paper overall
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    It said 298000 (or so) people per year have an X ray. So surely it is this number times 25 for the number of people getting an Xray? So out of 7,000,000 or so are people saying only 4 will get cancer? Seems a little low?
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    (Original post by Kingbradley6)
    It said 298000 (or so) people per year have an X ray. So surely it is this number times 25 for the number of people getting an Xray? So out of 7,000,000 or so are people saying only 4 will get cancer? Seems a little low?
    No, because the dose from an X-ray really isn't that significant.
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    The anser is 4.35

    For the realitivistic it was gamma = Erest + Ekinetic/Erest

    gamma = 1/root(1-v^2/c^2)
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    (Original post by Kingbradley6)
    It said 298000 (or so) people per year have an X ray. So surely it is this number times 25 for the number of people getting an Xray? So out of 7,000,000 or so are people saying only 4 will get cancer? Seems a little low?
    It's only an X-ray. Remember people will be assessed beforehand too, and if the risk is too high, they simply won't have a scan.
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    (Original post by Larry777)
    I said increase the cross sectional area and reduce the length of the magnetic circuit I pretty sure they are both correct as permeance= Permeability*Area/Length

    I think laminating the core would also possibly increase the permeability as it would decrease the eddy currents in the coil that reduce the overall magnetic flux passing through the iron core So don't worry!
    I said that Laminating the core doesn't increas permeance, it only reduces the amount of eddy currents.
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    (Original post by Summerdays)
    The anser is 4.35

    For the realitivistic it was gamma = Erest + Ekinetic/Erest

    gamma = 1/root(1-v^2/c^2)
    I can't believe I didn't see that. Argh I feel like an idiot now :L
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    What did you guys put for the 800 minimas.

    I ddi 2d = (800 + 1/2)lambda

    Not sure if this is correct.
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    (Original post by Summerdays)
    What did you guys put for the 800 minimas.

    I ddi 2d = (800 + 1/2)lambda

    Not sure if this is correct.
    800 plus 1/2? I thought it was 2d = nlambda...either way, something around the line of 500-ish nanometers for that laser?

    PS// Those prep Qs were gorge. Made Section C mostly dreamy. You = hero. ^^
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    (Original post by Swindan)
    It's only an X-ray. Remember people will be assessed beforehand too, and if the risk is too high, they simply won't have a scan.
    I think that's irrelevant? But if someone could explain their logic/calculations behind this question it would be appreciated.
 
 
 
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