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AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread] Watch

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    (Original post by knighty437)
    For the core unit:

    June 2010: What goes on in a nuclear reactor for induced fission
    June 2011: How pressure is exerted by gasses
    June 2012 Comparison of nuclei radius experiments, electron or alpha scattering
    June 2013: Determining a radioactive source
    June 2014: Half life of radioactive waste and how it should be stored.

    Those are the past 6 markers for anyone who's wondering.
    Do you think it'll be on the thermal side this year then?
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    Can someone please explain why in June 2014, question 1b(ii) we omit the binding energy of the neutrons from the calculation? Thanks
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    Is my derivation good enough?
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    (Original post by betbi3etwerrd)
    Is my derivation good enough?
    Yep. Here's what I'd say:

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    (Original post by Cruckshank)
    Can someone please explain why in June 2014, question 1b(ii) we omit the binding energy of the neutrons from the calculation? Thanks
    Neutrons dont have binding energy because they aren't binded to anything

    As said 1000 times in the last few pages already :lol:
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    (Original post by you-only-live-once)
    Yes true, I agree with the eye one - but I don't think we need to know much about how light ray get received by the brain? Also what would you say about endoscope + laparoscopic? I am thinking more of an X-ray question!
    By the brain bit I just mean optical nerves, details of action potential, flicker fusion etc.

    Endoscope, could talk about coherent and non-coherent bundles and functions, radius of curvature, details of refractive indexes. Laporoscopy, what is it, the advantages of it (less recovery time, no entrance wound, less time using hospital bed etc).

    I reckon X-rays will come up, could be absolutely anything mind - image intensifier plates, fluoroscopy intensifiers, advantages/disadvantages of different scans, voltage/current/energy/intensities relationship stuff, structure of x-ray machine... anything really!
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    Is there any sort of unofficial mark scheme for PHYA1? The PHYA4 was really well put together considering we were all students lol
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    So I just stumbled upon this in a revision guide, is this 100% the way you would ascertain the energy released in a reaction given the graph of binding energy per nucleon?

    E.g. instead of doing (BEPN of Helium-4) - (BEPN of He-3 + BEPN of He-2), you take the average between He-3 and He-2 to find the 'average increase', then multiply by the number of nucleons?
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    (Original post by Haza100)
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    So I just stumbled upon this in a revision guide, is this 100% the way you would ascertain the energy released in a reaction given the graph of binding energy per nucleon?

    E.g. instead of doing (BEPN of Helium-4) - (BEPN of He-3 + BEPN of He-2), you take the average between He-3 and He-2 to find the 'average increase', then multiply by the number of nucleons?
    This is very approximate result
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    What is the definition of parallax? I've seen a few of them around and I want to make sure I have the right wording because you know how picky they can be with their definitions
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    (Original post by Jimmy20002012)
    Anyone?


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    Try this, and let me know if you get the correct ratio
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    I feel like not having been able to revise Astro since before my first exam has affected me, less confident now than I was two weeks ago! Bricking it for this exam,
    Anyone else feel the same?
    All the numbers like masses of stars in main sequence etc have gone from my head
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    (Original post by _Caz_)
    What is the definition of parallax? I've seen a few of them around and I want to make sure I have the right wording because you know how picky they can be with their definitions
    Parallax itself is the shift in the apparent position of an object depending on the relative position between the object and observer.

    In terms of observing stars, it is used for estimating distances to nearby stars as the nearby stars shift in position relative to a backdrop of more distant stars.

    The angular shift in the line of sight from Earth to the object of interest over 6 months is halved to get the parallax angle, which is used to find the distance to the object.


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    Lamb is the constant of proportionality and the fraction of ..... I forgot the rest :/
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    (Original post by CD223)
    Parallax itself is the shift in the apparent position of an object depending on the relative position between the object and observer.

    In terms of observing stars, it is used for estimating distances to nearby stars as the nearby stars shift in position relative to a backdrop of more distant stars.

    The angular shift in the line of sight from Earth to the object of interest over 6 months is halved to get the parallax angle, which is used to find the distance to the object.


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    Ah okay - thank you!
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    (Original post by SuperMushroom)
    Can anyone explain question 2 a ii

    I dont get how you can answer it knowing only 1 piece of information?

    http://filestore.aqa.org.uk/subjects...1-QP-JUN14.PDF
    Use the equation N=No e^-yt

    Change it for what you've got, 0.375N=Ne^-yt

    Divide both sides by N to get 0.375=e^-yt

    Use your log laws to get t on its own as you worked y out in the previous question.
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    (Original post by thedontom)
    Lamb is the constant of proportionality and the fraction of ..... I forgot the rest :/
    is this the decay constant, lambda, you're talking about?

    if so, you can say the decay constant is the probability that nucleus will decay in a given unit time.
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    (Original post by AaronA330)
    Use the equation N=No e^-yt

    Change it for what you've got, 0.375N=Ne^-yt

    Divide both sides by N to get 0.375=e^-yt

    Use your log laws to get t on its own as you worked y out in the previous question.
    Thanks i have got it now
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    For Astrophysics tomorrow i think the 6 marker will be on the life cycle of a star and what happens 2 stars of different solar masses
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    (Original post by _Caz_)
    is this the decay constant, lambda, you're talking about?

    if so, you can say the decay constant is the probability that nucleus will decay in a given unit time.
    Lambda* xD Thank you!
 
 
 
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