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# OCR PHYSICS B G495~ 18th June 2015 AM ~ A2 Physics watch

1. (Original post by Mars256)
What are peoples suggestions to revise for section C?
These are what I plan on doing: (scroll to the g495 stuff)

2. Can anyone explain how this graph is formed, and why it has this shape and why nuclear radius affects where the minimum and maximum occur? All I know is that a minimum forms due to destructive interference of the electrons, acting as waves, with the protons.
3. (Original post by Nikeshp79)

Can anyone explain how this graph is formed, and why it has this shape and why nuclear radius affects where the minimum and maximum occur? All I know is that a minimum forms due to destructive interference of the electrons, acting as waves, with the protons.
Nuclear radius changes the spacing between nucleons does it not? Thus changing d will cause theta to change?

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4. (Original post by Rhetorical Hips)
Nuclear radius changes the spacing between nucleons does it not? Thus changing d will cause theta to change?

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Oh I've not come across that before! Thanks for letting me know However, the electrons don't pass through the nucleus in this experiment right? And it's to do with electrons, acting like a wave, and having a charge passing by a nucleus (electric field) causing the deflection angle to change. I just don't understand how the minima is formed if there is only one beam of electrons.
5. (Original post by Nikeshp79)
Oh I've not come across that before! Thanks for letting me know However, the electrons don't pass through the nucleus in this experiment right? And it's to do with electrons, acting like a wave, and having a charge passing by a nucleus (electric field) causing the deflection angle to change. I just don't understand how the minima is formed if there is only one beam of electrons.
Electrons act as a wave, when a wave hits lots of little circles blocking its paths you get diffraction around the edges of circles causing an interference pattern which is it a lot of concentric rings of maxima and minima, the spacing is based on the wavelength of the wave and the diameter of the circles blocking it (diameter of atoms). So you look at sin(theta) for the first minima and take into account the wavelength of the electrons and then you can calculate the radius of a nucleus
6. (Original post by bafid)
Electrons act as a wave, when a wave hits lots of little circles blocking its paths you get diffraction around the edges of circles causing an interference pattern which is it a lot of concentric rings of maxima and minima, the spacing is based on the wavelength of the wave and the diameter of the circles blocking it (diameter of atoms). So you look at sin(theta) for the first minima and take into account the wavelength of the electrons and then you can calculate the radius of a nucleus
Excellent, thanks!
7. Is it just me or does hardly ANYONE do OCR Physics B? Maybe it's for a reason...
8. (Original post by ashysmithy105)
Is it just me or does hardly ANYONE do OCR Physics B? Maybe it's for a reason...
Guess it's one of the harder subjects possibly by a fair bit, and quite a few drop out after AS
9. Tomorrow gonna spend the whole day doing Physics revision. Have a bunch of past papers planned + some lens questions from the G491 stuff for section C. Anyone got any other suggestions as to how to consolidate/improve understanding?

I need around 85/100 for an A overall

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11. (Original post by Mutleybm1996)

I need around 85/100 for an A overall

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Just stay calm and focused in the exam, don't think about it being the chance you must get right. Just push that all away and take in the information.

I panicked in all my exams except chemistry last year, mainly due to not focusing and wanting to achieve very high marks. In combo with not enough revision, it didn't work out of course

Just do your best, nothing more can be asked of you
12. (Original post by Mutleybm1996)

I need around 85/100 for an A overall

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Keep calm! You can do it, your brain will get you through this
13. (Original post by ashysmithy105)
Is it just me or does hardly ANYONE do OCR Physics B? Maybe it's for a reason...
It's rubbish course compared to OCR A for example, the textbook is dreadful and the amount of stupid wording is probably where most people lose marks...

Schools probably avoid it for those reasons!
14. Just had a look through the Signalling and Images section of AS stuff. There doesn't seem to be that much there we need to know for section C.
15. Is anyone else using the OCR A textbook to revise?

Does anyone have any tips for the section C? Can they throw anything not in our spec at us? Like the magnification of two lenses and stuff

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16. (Original post by Iridann)
Tomorrow gonna spend the whole day doing Physics revision. Have a bunch of past papers planned + some lens questions from the G491 stuff for section C. Anyone got any other suggestions as to how to consolidate/improve understanding?
Just you wait....

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17. (Original post by Tibbz2)
It's rubbish course compared to OCR A for example, the textbook is dreadful and the amount of stupid wording is probably where most people lose marks...

Schools probably avoid it for those reasons!
Yeah the wording is terrible, and the mark scheme can be picky!
18. (Original post by RealTime)
Yeah the wording is terrible, and the mark scheme can be picky!
I hear G484 was horrible this year
With even top students barely scraping 40

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19. I know for a fact that this year's year 12s are studying a different board now, we're the last year in this college to do ocr b...
20. How/why does the emission of secondary electrons from the sample limit the resolution of the electron microscope?
Also, is the resolution essentially determined by the size of the diffraction spots, which theoretically could be as small as the wavelength of the electrons? Can't quite get my head around these ideas which seem to be suggested by the questions on P1, so if someone could clear it up for me that'd be great

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