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general Phy 4 and 5 concerns (edexcel) watch

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    hello,

    started this because i didn't want to create multiple threads. got a number of quetions and wondering whether anyone can help:

    1) Are we required to know how so experimentally demonstrate teh charge stored in a capacitor to to describe how to measure it
    2) are we required to demonstrate the photoelectric eperiment and how to calculate the stopping potential
    3) what definitions do we need to know for phy 4 and 5
    4) in unit 4 when we pass light through a single source (laser or otherwise) what intensity pattern do we get - bit confused because for layer intensity pattern there is only one mode, i.e. the central maximum, but i recall some markschemes having two smaller maxima on either side, and dont know the reason for this, and am not sure whether this applies to incoherent single sources or what
    5)when and when not can we use the eqtn: λ/s = x/D

    thats all for now i think - will post more if i get stuck again

    pk
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    1. yes
    2. yes
    3. quite a lot
    4. you have the main one and then two smaller peaks on each side. this is because the "wavelets" coming from the same slit interfere as well.
    5. you can use it for all calculations with sound and EM radiation, for the double slit experiment, ie as long as the sources are coherent and have the same amplitude and frequency.
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    does anyone kno if we need to know the em-spectrum (all the wavelengths, frequencies etc ... like its in that table in the nelson (nas) books)?
    thanks for any help
    ....... hope the answer is no, aint got any time to learn stuff like that at this stage :eek:
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    (Original post by mik1w)
    1. yes
    2. yes
    3. quite a lot
    4. you have the main one and then two smaller peaks on each side. this is because the "wavelets" coming from the same slit interfere as well.
    5. you can use it for all calculations with sound and EM radiation, for the double slit experiment, ie as long as the sources are coherent and have the same amplitude and frequency.
    is that only for non lasers? - for laysers the graph has one maximum and then dips down on eitherside - how do you now when to draw either one?
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    (Original post by sumitk87)
    does anyone kno if we need to know the em-spectrum (all the wavelengths, frequencies etc ... like its in that table in the nelson (nas) books)?
    thanks for any help
    ....... hope the answer is no, aint got any time to learn stuff like that at this stage :eek:
    i dnt think u do...but i fudged up 7 marks in jan bcos i didnt and tuk the wavelngth to b micorwaves when it was visible..
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    it happens for all EM radiation. they sometimes omit it from the markscheme because the scale of the graph you have to draw on is too small
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    (Original post by mackin boi)
    i dnt think u do...but i fudged up 7 marks in jan bcos i didnt and tuk the wavelngth to b micorwaves when it was visible..
    but if u needed to kno part of it for jan04 wouldnt that mean u need to kno it for 2morow :eek:
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    (Original post by mik1w)
    it happens for all EM radiation. they sometimes omit it from the markscheme because the scale of the graph you have to draw on is too small
    think you are wrong there - bcause for microwaves from a laser, there is only one peak - not this wavelet thing
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    that's because of the setup of the experiment, it still happens.
    and if you think I am wrong, why are you asking about it?

    there is no difference between light and microwaves except the wavelength, so the angle will be much greater as the wavelength is a lot longer.
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    (Original post by mik1w)
    that's because of the setup of the experiment, it still happens.
    and if you think I am wrong, why are you asking about it?

    there is no difference between light and microwaves except the wavelength, so the angle will be much greater as the wavelength is a lot longer.
    askign because there are two different intensity graphs!! one has only one peak, and the other has one peak in the middle and two peaks of smaller amplitude on either side, and they are both fro single slits, and i've no idea why there is a difference, that's what

    can anyone explain this weird phenomonon?
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    I have already said..

    "they sometimes omit it from the markscheme because the scale of the graph you have to draw on is too small"
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    (Original post by mik1w)
    I have already said..

    "they sometimes omit it from the markscheme because the scale of the graph you have to draw on is too small"
    have you got a copy of the jan 2003 paper? have a look at question 6 (the last part - tell me what you make of it)

    cheers
    PK
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    in that case you would not include them because of the scale, as you can see further from the middle the maximum points are falling in height, but not gone to zero yet so you wouldn't include it - it is off the scale.
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    (Original post by sumitk87)
    does anyone kno if we need to know the em-spectrum (all the wavelengths, frequencies etc ... like its in that table in the nelson (nas) books)?
    thanks for any help
    ....... hope the answer is no, aint got any time to learn stuff like that at this stage :eek:
    well it says in the nas revision guide u need to kno the wavelengths for the 'seven main regions of em spectrum'.
    its not that hard...once u kno the wavelength or frequency, u can use c=fλ to get the freq/wavelength
    i personally find it easier to remember the frequencies n work out the wavelength if needed
    questions have come up in previous yrs..u probably shudnt risk it
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    you do need to know then, it relied ion GCSE knowledge whic is the EM spectrum, only takes 5 minutes to learn, itll be the easiest marks you get.

    radio - HF - UHF - microwaves - IR - visible - UV - x-rays - gamma rays
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    (Original post by hajira)
    well it says in the nas revision guide u need to kno the wavelengths for the 'seven main regions of em spectrum'.
    its not that hard...once u kno the wavelength or frequency, u can use c=fλ to get the freq/wavelength
    i personally find it easier to remember the frequencies n work out the wavelength if needed
    questions have come up in previous yrs..u probably shudnt risk it
    thanks ill try learning the main regions now
    hopefully remember it for 2morow although if i dont kno ill guess microwaves or UV
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    (Original post by Phil23)
    have you got a copy of the jan 2003 paper? have a look at question 6 (the last part - tell me what you make of it)

    cheers
    PK
    hav u got the mark scheme to that?
    iv got a handwritten one n cant watsoever make out what the first point is, the other being 'max at 0'
    plz if u can read that tell me
    :rolleyes:
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    All you need to know is

    Ray Michaels Invented Very Useful X-Rated Games

    Radio -- 10^2m to 10^0m
    Microwaves -- 10^-2m
    Infra Red -- 10^-4m to 10^-6m
    Visible Light -- 400nm (Violet) to 700nm (Red)
    Ultra Violet -- 10^-8m
    X-Ray -- 10^-9m
    Gamma -- 10^-14m
    Online

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    When does it change from mirowaves to radio waves?
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    xrays is 10^-11m to 10^-13m.
 
 
 
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