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

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    (Original post by CD223)
    "Brightness". Although equally I've seen them use intensity just as much before.


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    Ok, cheers. I think I get that now.
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    What does the first minimum in electron diffraction represent ?


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    Does anyone know why during electron diffraction the deflection is purely down to diffraction and not the positively charged nuclei affecting the paths of the electrons?
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    does anyone have a list of all the keywords and their definitions that we need for nuclear&thermal section
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    (Original post by coqthepoliceman)
    does anyone have a list of all the keywords and their definitions that we need for nuclear&thermal section
    Try the book glossary lol?
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    (Original post by coqthepoliceman)
    does anyone have a list of all the keywords and their definitions that we need for nuclear&thermal section
    Here you go
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  1. File Type: docx Unit_5_definitions.docx (15.6 KB, 142 views)
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    (Original post by gcsestuff)
    What does the first minimum in electron diffraction represent ?


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    Electrons behave like waves with a de Broglie wavelength - this minimum represents where destructive interference first takes place where beams superpose on top of one another (see unit 2 notes). All you need to know is that the first minimum is where \sin \theta = \frac{1.22 \lambda}{D}.


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    does anyone have the specimen paper for unit 5 and the astrophysics section along with a mark scheme please
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    thanks
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    (Original post by CD223)
    Electrons behave like waves with a de Broglie wavelength - this minimum represents where destructive interference first takes place where beams superpose on top of one another (see unit 2 notes). All you need to know is that the first minimum is where \sin \theta = \frac{1.22 \lambda}{D}.


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    Thanks


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    (Original post by InNeedOfHelpASAP)
    Hi guys, I'm a private candidate and have been studying from home. I've learned the whole Unit 5 syllabus and have practiced all the past paper exams because I'm not quite sure which papers I'm supposed to take and why there are so many?:| If anyone could steer me in the right direction, that would be great because I think I've probably covered more than I needed to?
    This doesn't sound good. When you went to apply to take the unit 5 exam did you not specify which optional topic you would be doing? Considering there's two parts to Unit 5.
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    Can't wait to get this exam out of the way. Been cramming like crazy for it over the last 2 days. Plz low grade boundaries plz
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    (Original post by 123defort)
    This doesn't sound good. When you went to apply to take the unit 5 exam did you not specify which optional topic you would be doing? Considering there's two parts to Unit 5.
    No you get given all the papers I think.
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    (Original post by EconFan_73)
    Does anyone know why during electron diffraction the deflection is purely down to diffraction and not the positively charged nuclei affecting the paths of the electrons?
    I think that:
    1) High speed electrons show wave-particle duality, this is why they are diffracted by the nucleus which we assume to be a circular appature.
    2) Electrons have less charge than an alpha and so the electro-static force has less affect.
    3) The electrons move faster than alphas I believe, meaning there is less time that the force acts on the electron.
    But I think that we just say they act as a wave that is no affected by the charge of the nucleus.
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    Anyone wanting to revise inversion tube experiments.
    June 05- unit2 old spec question 4

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    (Original post by betbi3etwerrd)
    No you get given all the papers I think.
    I don't think they give them all because then they would have to order all the papers for every single student. Colleges already usually preset the option therefore only need that option paper. Because I'm doing it privately as well I had to specify which option I was doing so the college would know which optional paper they need.
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    (Original post by SuperMushroom)
    We will most certainly be getting the replacement paper
    Do you think it'll be more difficult than usual?
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    (Original post by CD223)
    Electrons behave like waves with a de Broglie wavelength - this minimum represents where destructive interference first takes place where beams superpose on top of one another (see unit 2 notes). All you need to know is that the first minimum is where \sin \theta = \frac{1.22 \lambda}{D}.


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    Why is it 1.22? I've been trying to google this and can't find anything on it.
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    Anyone else think the grade boundaries will increase this year? Last year they were so low lol

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    (Original post by zarifina)
    Why is it 1.22? I've been trying to google this and can't find anything on it.
    I explained this the other day - it's not a reason you need to know.

    http://www.quora.com/Where-does-this...its-derivation


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