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Edexcel Physics Unit 2 "Physics at work" June 2013 watch

  • View Poll Results: The last question - Does resistance increase or decrease?
    It increases ( using V=IR or some other method)
    70.73%
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    (Original post by Randy123)
    hey, does anyone on here know whether we need to learn about the evidence which support the wave/particle theory or whether we only need to know how to explain the evidence?
    Do both since Edexcel may give you a big bomb surprise!

    Learn observations of the photoelectric effect and be able to say why it supports particle model and not the wave model of light.
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    could someone please explain to me the observation of the photoelectric effect...i understand why it supports the particle model of light and not the wave but if someone could summarise the observation and experiment itself i would be grateful
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    Anyones got jan 2013 paper unit 2?????
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    (Original post by krisshP)
    Do both since Edexcel may give you a big bomb surprise!

    Learn observations of the photoelectric effect and be able to say why it supports particle model and not the wave model of light.
    thank you..hopefully they will just ask how the photoelectric effect supports it haha also do you know if we need to know any other observations like the double slit experiment
    thankyou
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    (Original post by lob.dub)
    Anyones got jan 2013 paper unit 2?????
    http://www.thestudentroom.co.uk/show....php?t=2262586
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    (Original post by lob.dub)
    Anyones got jan 2013 paper unit 2?????
    http://www.thestudentroom.co.uk/show....php?t=2262586
    (Original post by Randy123)
    could someone please explain to me the observation of the photoelectric effect...i understand why it supports the particle model of light and not the wave but if someone could summarise the observation and experiment itself i would be grateful
    Look at the mark scheme for the January 2013 unit 2 paper now.
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    Thats the economics paper, unless I've missed it somewhere in the post?
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    (Original post by Jaydude)
    Thats the economics paper, unless I've missed it somewhere in the post?
    Oops sorry
    http://www.mediafire.com/?5djntd8dd7ykb
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    Thanks
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    Name:  phys ms.png
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Size:  45.3 KBBit confused about Jan 11, 19aii) - attached the question and MS but I don't understand why you divide the wavelength from i) by 4? ThanksName:  phys q.png
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    (Original post by ambbs)
    Name:  phys ms.png
Views: 139
Size:  45.3 KBBit confused about Jan 11, 19aii) - attached the question and MS but I don't understand why you divide the wavelength from i) by 4? ThanksName:  phys q.png
Views: 152
Size:  51.5 KB
    Divide the wavelength by 2, to find the minimum length for it to be out of phase, and then since that length is the distance there and back, you have to divide by 2 again to find the distance between the two points


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    (Original post by JoshThomas)
    Divide the wavelength by 2, to find the minimum length for it to be out of phase, and then since that length is the distance there and back, you have to divide by 2 again to find the distance between the two points


    Posted from TSR Mobile
    Could you explain this question? I get part A (i) but not part (ii)
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    (Original post by JoshThomas)
    Divide the wavelength by 2, to find the minimum length for it to be out of phase, and then since that length is the distance there and back, you have to divide by 2 again to find the distance between the two points


    Posted from TSR Mobile
    Ah I see, thank you! I didn't grasp the idea that the length was the distance there AND back which is where I got stuck cheers! Run out of rep but would pos rep you if I could
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    (Original post by CoolRunner)
    Could you explain this question? I get part A (i) but not part (ii)
    Which questionnn?

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    (Original post by StUdEnTIGCSE)
    Well you can show it by calculus

    Spoiler:
    Show



     





V=E-Ir



VI=I(E-Ir)



P=VI=EI-I^2R



therefore \dfrac{dP}{dI}=E-2Ir





At max P,



 \dfrac{dP}{dI} =0



0=E-2Ir



2Ir=E



I= \dfrac{E}{2r} \ast



BUT:



V=E-Ir and V=IR



V=E-Ir=IR



E=I(R+r)



I= \dfrac{E}{R+r} \bullet



at max P,





\ast=\bullet  







Therefore 2r=R+r



R=r

    that was quite neat, how do you know this stuff?
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    (Original post by Boy_wonder_95)
    that was quite neat, how do you know this stuff?
    It's on wikipedia
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    (Original post by Boy_wonder_95)
    that was quite neat, how do you know this stuff?
    (Original post by justinawe)
    It's on wikipedia
    Me no plagiarise from Wikipedia

    My twin bro was reading the textbook and all of a sudden challenged me to prove it. So I proved it. I just had to take out the textbook and transfer it in.

    Its not a valid proof anyway. :ahee:

    Edit: I can upload a pic of my original I from the textbook itself if you are bothered that's the spirit..

    Posted from TSR Mobile
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    (Original post by StUdEnTIGCSE)
    Me no plagiarise from Wikipedia

    My twin bro was reading the textbook and all of a sudden challenged me to prove it. So I proved it. I just had to take out the textbook and transfer it in.

    Its not a valid proof anyway. :ahee:

    Edit: I can upload a pic of my original I from the textbook itself if you are bothered that's the spirit..

    Posted from TSR Mobile
    Yeah, looking at Wikipedia, the calculus-based proof there is different, so can't be plagiarised
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    Just to clarify, does refraction only happen from a less dense to more dense medium?
    And TIR only occurs in the more dense medium?

    Thanks

    EDIT: What is it you put on the top and bottom of the Snell's law equation, like when do you know what, 'velocity', for example to put on the numerator or denominator ?

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    (Original post by Branny101)
    Just to clarify, does refraction only happen from a less dense to more dense medium?
    And TIR only occurs in the more dense medium?

    Thanks

    EDIT: What is it you put on the top and bottom of the Snell's law equation, like when do you know what, 'velocity', for example to put on the numerator or denominator ?

    Posted from TSR Mobile
    Yes, TIR occurs in the denser medium.

    Not sure what you mean by refraction. Refraction can occur when going from a more dense to less dense medium OR from less dense medium to more dense medium.

    U=velocity1/velocity2

    Or

    U=sin I/sin r

    Both equations should give the same refractive index.

    If they give you velocities, use U=velocity 1/velocity 2. If they give angles of incidence and refraction, use U=sin I/sinr
 
 
 
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