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2016 | OCR A2 Advancing Physics B | G494 & G495 | 20th & 28th June Watch

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    (Original post by Wunderbarr)
    UwotM9 ?

    I highly doubt you need to know that.
    Ok, because all i've got in my notes is 'need to know absolute luminosity' and i don't remember the teacher saying anything else about it
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    (Original post by notrodash)
    Hey we're doing the same exams then! We were literally doing COMP3 theory up until the last day of teaching and even then we missed out details here or there. My college has the textbooks available in the library so I took one out over half term and made notes on the stuff that we didn't cover in enough detail. The week after next will be interesting for me since the FP3 and S2 exams clash. *sigh*

    Wow, that's funny. Ouch, exam clashes are bad. I had one last year for COMP1 and WJEC ICT (because putting ICT and Computing on the same day is a great idea, right? Nobody ever takes both those subjects), and basically after COMP1 was done, we were forced to stay in the room, then literally herded around like cattle. If one of us needed the toilet, we all had to walk them there so the teacher could keep an on us. It was degrading and awkward. Have fun!

    Also, does anybody know any other similar papers to attempt? The old ones are far too easy, and there aren't many new ones (i.e. 2010-2015) and I can't attempt 2015 because I don't have the mark scheme. Anybody do have the mark scheme?

    Thanks!
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    (Original post by Wunderbarr)
    UwotM9 ?

    I highly doubt you need to know that.
    never seen it come up, so its probably a good idea to know about it. for G495 make sure you know milikans oil drop experiments as its in the syllabus but has never come up
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    There you go guys, i would use this thread as well for G495
    http://www.thestudentroom.co.uk/show...rimary_content
    Attached Images
  1. File Type: pdf RGch10.pdf (400.5 KB, 126 views)
  2. File Type: pdf RGch11.pdf (389.8 KB, 101 views)
  3. File Type: pdf RGch13.pdf (370.2 KB, 84 views)
  4. File Type: pdf RGch14.pdf (175.2 KB, 112 views)
  5. File Type: pdf Qch10-14.pdf (609.0 KB, 124 views)
  6. File Type: pdf Ach10-14.pdf (170.9 KB, 86 views)
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    (Original post by brouser79)
    Ok, because all i've got in my notes is 'need to know absolute luminosity' and i don't remember the teacher saying anything else about it
    Slight apology but after looking through the CGP book, it mentions apparent brightness and luminosity, so it may perhaps come up as a method for calculating astronomical distances.

    However it is not in too much detail (such as calculating luminosity).

    It doesn't go into more detail than at Triple Science GCSE (for OCR 21st Century P7 at least).
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    Can someone explain relativistic doppler shift to me? It's never come up (afaik) and the explanation in the Advancing Physics revision guide is vague and has broken formatting.

    It's also entirely absent from the new spec textbook.
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    Picture a race car going past you, when it comes towards youit is a very high pitched sound, then when it goes past you it becomes lowerpitched. The high pitch is due to a high frequency as when something is moving towards you, its frequency increases and its wavelength decreases. This is blue shift. Now, the race car sound decreases in frequency when it moves pastyou and increases in wavelength shown by the lower pitched sound, its movingaway from you and is red shifted. This is the basic Doppler shift and is a property of all waves. You can use itto find the speeds of objects since v/c = change in wavelength divided by theoriginal wavelength, frequency can also be used in place of wavelength. In therevision guide the Doppler effect is : thechange of frequency of waves from a source due to relative motion between thesource and the observer. I’d use this as the concise definition if an exam question asks for it.

    Something which increases in wavelength is red shifted becauseit goes to the red end of the spectrumof light as things like microwaves radio etc have longer wavelengths. Thenblue shift goes to the blue end of lightso it increases in frequency instead since gamma x ray etc are of highfrequency which is why they are harmful since they will carry more energy. Cosmological red shift is interpreted slightly differently. Visualise two points separated by somedistance d. As space-time expands (i.e. after the big bang) the distance dbetween these two points increases as space spreads out like a wave. Relativeto some observer, say if someone was closer to one point than the other e.g.someone on the moon and you are looking at earth and mars as the two points. Ifspace time expands, then the earth is blue shifted as its moving towards you,whereas mars is moving away and is red shifted.

    You now have the equation v=Hd, where H is the Hubble constant,this applies to EM waves and not sound or other waves. This shows that the recessional velocity of an object is proportionalto its distance from an observer. Recessional velocity is how fastsomething moves away from you so it shows that if one object is further awayfrom you than another object, e.g. the earth and mars. Then mars will have agreater recessional velocity as it is further away, therefore objects that havemore red shift, recede at greater speeds.

    I have used the moon earth and mars as examples. This is notactually true as they lie in the Sun's gravitational field which means they DONOT move from each other, they stay at a fixed radius from each other. I wasjust using these as an example of two objects that recede that are NOT in agravitational field. Hope this helps
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    (Original post by kennz)
    Picture a race car going past you, when it comes towards you it is a very high pitched sound, then when it goes past you it becomes lower pitched. The high pitch is due to a high frequency as when something is moving towards you, its frequency increases and its wavelength decreases. This is blue shift. Now, the race car sound decreases in frequency when it moves past you and increases in wavelength shown by the lower pitched sound, its moving away from you and is red shifted. This is the basic doppler shift and is a property of all waves. You can use it to find the speeds of objects since v/c = change in wavelength divided by the original wavelength, frequency can also be used in place of wavelength

    Cosmlological red shift is interpreted slightly differently. Visualise two points seperated by some distance d. As space-time expands (i.e. after the big bang) the distance d between these two points increases as space spreads out like a wave. Relative to some observer, say if someone was closer to one point than the other e.g. someone on the moon and you are looking at earth and mars as the two points. If space time expands, then the earth is blue shifted as its moving towars you, whereas mars is moving away and is red shifted.

    You now have the equation v=Hd, where H is the hubble consant. This shows that the recessional velocity of an object is proportional to its distance from an observer. recessional velocity is how fast something moves away from you so it shows that if one object is further away from you than another object, e.g. the eart and mars. Then mars will have a greater recessional velocity as it is further away, therefore objects that have more red shift, recceed at greater speeds.

    I have used the moon earth and mars as examples. This is not actually true as they lie in the Sun's gravitational field which means they DO NOT move from each other, they stay at a fixed radius from each other. I was just using these as an example of two objects that recceed that are NOT in a gravitational field.

    Hope this helps
    All of your examples appear to be non-relativistic (which I'm fine with), but there's a relativistic doppler shift equation which we covered in class but I don't understand how it's derived.

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    (Original post by notrodash)
    All of your examples appear to be non-relativistic (which I'm fine with), but there's a relativistic doppler shift equation which we covered in class but I don't understand how it's derived.

    This should help:

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    (Original post by notrodash)
    All of your examples appear to be non-relativistic (which I'm fine with), but there's a relativistic doppler shift equation which we covered in class but I don't understand how it's derived.

    Ah ok , well look at the revision guide I have attached,
    http://www.school-for-champions.com/...m#.V2asUqKrG9Y

    All this stuff comes from the 'light clock' thought experiment where you have a light source bouncing off a mirror when the reference frames are at rest and not at rest. What happens in most equations is that when you have something travelling at such high speeds, the relativistic must be taken into account since it becomes so big so you just mulitply it by the equation. If I'm honest, you just need to be able to use these equations, not derive them.

    either way, the revision guide section for doppler shift should help
    sorry it took so long, i was converting the file to make it smaller and I have deleted some stuff so I can upload it
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  7. File Type: pdf gdjn.pdf (961.2 KB, 91 views)
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    Does anyone have the June 2015 papers?

    - especially for Rise+Fall tomorrow
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    (Original post by zackdove)
    Does anyone have the June 2015 papers?

    - especially for Rise+Fall tomorrow
    See attached.
    Attached Images
  8. File Type: pdf G494_June_2015_Paper.pdf (491.1 KB, 134 views)
  9. File Type: pdf G494_June_2015_Mark_Scheme.pdf (165.8 KB, 124 views)
  10. File Type: pdf G495_June_2015_Paper.pdf (663.1 KB, 91 views)
  11. File Type: pdf G495_June_2015_Pre_Release.pdf (755.0 KB, 69 views)
  12. File Type: pdf G495_June_2015_Mark_Scheme.pdf (107.4 KB, 124 views)
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    Best of luck to you all tomorrow. I'm kinda worried that I'm still "learning" new things (i.e. reminding myself of things). Are binary star systems in the syllabus, or was that just a one-time thing from last year's paper? (which annoyingly doesn't have a mark scheme)
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    (Original post by Polyrogue)
    Best of luck to you all tomorrow. I'm kinda worried that I'm still "learning" new things (i.e. reminding myself of things). Are binary star systems in the syllabus, or was that just a one-time thing from last year's paper? (which annoyingly doesn't have a mark scheme)
    they're not in the syllabus but OCR can put things in outside the syllabus, as long as they use the ideas we have learnt.
    If you think about that question, it makes sense without knowing much about binary stars. Since Binary stars are pretty much identical, they should have the same equipotential lines.
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    (Original post by kennz)
    they're not in the syllabus but OCR can put things in outside the syllabus, as long as they use the ideas we have learnt.
    If you think about that question, it makes sense without knowing much about binary stars. Since Binary stars are pretty much identical, they should have the same equipotential lines.
    Thanks. To be clear, was the answer to that question B?
    A is obviously wrong, D is insane, and C seemed unlikely.
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    (Original post by Polyrogue)
    Thanks. To be clear, was the answer to that question B?
    A is obviously wrong, D is insane, and C seemed unlikely.
    yeah B
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    (Original post by kennz)
    yeah B
    Great, thanks.
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    (Original post by Polyrogue)
    Best of luck to you all tomorrow. I'm kinda worried that I'm still "learning" new things (i.e. reminding myself of things). Are binary star systems in the syllabus, or was that just a one-time thing from last year's paper? (which annoyingly doesn't have a mark scheme)
    I think the main point of that question was to test your understanding of how equipotential lines form around masses and what they actually show.

    But yes!

    Here's to it going well, and

    May you leap no further than the laws of this universe!
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    May the force be with us :charm::charm:
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    Was struck with a splitting headache just before the exam :'( had to battle through it the entire time. I think I did quite well, but given the constant throbbing pain I feel right now I can't be sure.
 
 
 
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