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

1. (Original post by _Caz_;[url="tel:57110427")
57110427[/url]]
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Thanks Caz; I think me and you have the same exam timetable by the way...
2. (Original post by Fvthoms)
Thanks Caz; I think me and you have the same exam timetable by the way...
I kinda noticed you keep popping up everywhere haha! Have you got fp2 on Monday as well?

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3. (Original post by Me123456789)
Oh, that makes more sense now, thanks
No problem!

(Original post by dannyoboy007)
How do I solve these sorts of questions? Attachment 430431
The ratio of number of photons incident on the detector to the number of photons produced by the source is equal to the ratio of their two surface areas.

(Original post by frankiejayx)
Is magnification Beta / Alpha ?

Also is it only mirrors that suffer from spherical abberation??
Yeah magnification can be expressed as:

• Image height divided by object height
• Image distance divided by object distance
• Angle subtended by the image to the eyepiece lens divided by the angle subtended by the object to the unaided eye (beta over alpha!)

Reflecting telescopes are the only ones to suffer from spherical aberration but this can be solved by using a parabolic mirror.

(Original post by JJBinn)
How do you know that? It says the molten lead starts at 327 and the iron finishes at 84. I don't understand why you can deduce that the final temperature is therefore 327-84? It's probably really basic just don't see it
It says that they reach thermal equilibrium meaning they end up at the same temperature and there's no net transfer of heat energy between them. As such, the final temperature of the molten lead (which is now solid) is 84 degrees as this is the same as the final temperature of the iron mould.

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4. Thie iron finishes at 84 but the Molten lead does not finish at 84 though if it's change in temperature is 327-84? That would be 243? So confused haha.

Just realised how much of an idiot I am, that's the difference between 84 and 327 ahaha what a bad mistake
5. (Original post by _Caz_)
I kinda noticed you keep popping up everywhere haha! Have you got fp2 on Monday as well?

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Nah, S2 and then I'm finished. To be honest though, in my mind I'll be done once PHYA5 is over.
6. Can anyone explain how the electron diffraction experiment shows how big or small a nucleus radius is? especially how the minimum angle is relevant.
7. (Original post by CD223)
Reflecting telescopes are the only ones to suffer from spherical aberration but this can be solved by using a parabolic mirror.

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Don't refracting telescopes too?
8. (Original post by Fvthoms)
Nah, S2 and then I'm finished. To be honest though, in my mind I'll be done once PHYA5 is over.
I've not done any fp2 revision in a while to be honest so I've got my work cut out after physics 5. Good luck for s2, I mean I'm not sure what board you're on but my s2 paper a few weeks ago was nice enough so I'm hoping its the same for you! How are you feeling for physics 5?

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9. For the inverse square law... Is d always in parsecs?
10. (Original post by _Caz_)
I've not done any fp2 revision in a while to be honest so I've got my work cut out after physics 5. Good luck for s2, I mean I'm not sure what board you're on but my s2 paper a few weeks ago was nice enough so I'm hoping its the same for you! How are you feeling for physics 5?

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How I feel for Unit 5... driven is the word. Went into the PHYA4 overconfident and unfocused; did well in the MC (23/25) but made a mistake on pretty much every written question . Need to get those marks back to keep the A.

I haven't looked at S2 for two months; done a past paper a few days ago and scraped the boundary for an A, but I definitely have my work cut out me in Stats aswell.
11. (Original post by ubisoft)
Yeah but I said same isotopes? All same isotopes have same decay constant?
For any one particular isotope, it will always have the same decay constant and half life.

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12. (Original post by muyiwaaiyenuro)
Can anyone explain how the electron diffraction experiment shows how big or small a nucleus radius is? especially how the minimum angle is relevant.
There's a formula, sinx=1.22lambda/d where d is the diameter of the nucleus, lambda is the wavelength of the electron beam and x is the angle between the first minimum and the line of the electron beam.
13. (Original post by Fvthoms)
How I feel for Unit 5... driven is the word. Went into the PHYA4 overconfident and unfocused; did well in the MC (23/25) but made a mistake on pretty much every written question . Need to get those marks back to keep the A.

I haven't looked at S2 for two months; done a past paper a few days ago and scraped the boundary for an A, but I definitely have my work cut out me in Stats aswell.
Good luck! I think you'll manage the A! (For both exams that is)

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14. In using the formulae for kinetic energy of gas's and molecules, can somebody clarify the crms speed? If we are given a speed called the root mean square speed, we square this before using it in the formulae? And if we are given the mean square speed, we can use it straight away right?

What about if it just said the average speed of the molecules is x. Would you square x or would you be able to put it straight in?
15. (Original post by _Caz_)
Good luck! I think you'll manage the A! (For both exams that is)

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You have more faith in my abilities than I do . Thank you though, and good luck for tomorrow and FP2!
16. (Original post by JJBinn)
There's a formula, sinx=1.22lambda/d where d is the diameter of the nucleus, lambda is the wavelength of the electron beam and x is the angle between the first minimum and the line of the electron beam.
I know that, but is there any derivation/reason for why this is?
17. (Original post by muyiwaaiyenuro)
I know that, but is there any derivation/reason for why this is?
Well there will be but it's not required for the exam, just make sure you understand the formula and can describe how it can be used in an experiment to determine the radius/diameter of a nucleus
18. (Original post by JJBinn)
Well there will be but it's not required for the exam, just make sure you understand the formula and can describe how it can be used in an experiment to determine the radius/diameter of a nucleus
Nice, thanks mate
19. Hi I was just wondering could someone help me with this. I've done most of it right. The previous part I got and I got half way through part ii) But when it asks for how many tines better it is I don't know where they got the 1.2x10-4 part from in the working? I've attached pictures of the question and the answers in this post. If anyone has any idea where they got the 1.2x10-4 from it would be a great help because I've tired everything. I've even tried just mindlessly trying to multiply/divide numbers from the question but I can't get 1.2x10-4 out? What am I missing?

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Attached Images

20. Can someone help me with 3bi on june 2012, no idea where that method comes from

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